Incorrectly regarded as goofs

People exposed to the vacuum of space do not freeze in a matter of seconds/minutes. In a vacuum the only way to lose (or gain) body heat is through thermal radiation. It would take hours and hours. This is what makes a vacuum a good insulator. In fact, if you were to float in sunlight you'd sooner cook than freeze.

Correction: The pressure is important: Your eyes, if left open, would basically boil and surface freeze because of lack of pressure on the liquid. Your tongue would be susceptible as well. The pressure issue would also make it impossible to hold air in your lungs, so you would pass out within a minute, but likely much sooner: "In 1965, while performing tests at the Johnson Space Center, a subject was accidentally exposed to a near vacuum (less than 1 psi) when his space suit leaked while in a vacuum chamber.

He did not pass out for about 14 seconds, by which time unoxygenated blood had reached his brain. Technicians began to repressurize the chamber within 15 seconds and he regained consciousness at around the equivalent of 15,000 feet of altitude. He later said that his last conscious memory was of the water on his tongue beginning to boil. So, there's at least one data point about what it's like to be in a vacuum. It won't be pleasant, but it won't be like the movies, either."

Continuity

At the begin Ego is running down through the woods with Meredith, in a split second long shot she is wearing Ugg Boots however, in the later shots of her feet she is wearing a pair of heels.

Incorrectly regarded as goofs

Yondu tells Rocket he found him by adding a tracer device to Peter's ship "during the war with Xandar", most likely referring to the climax battle of the first movie, even though that ship was destroyed in that battle and later rebuilt by Nova Corp. However, it is explicitly stated that Nova Corp was able to salvage parts of the original ship and incorporate them into the new one (including Peter's cassette player). Evidently, one of those parts contained the tracer.

Incorrectly regarded as goofs

When Peter's ship is crashing into the forest on Berhert, Drax is still outside, being pulled along on a tether. When the ship hits the trees, it slows down. If Drax's speed remains constant, he should be pulled closer to the ship, perhaps even crashing into the cargo hold, yet the tether remains fully stretched (so much so that it eventually breaks off). This is because Drax also slows down by hitting the trees himself and due to air resistance.

Continuity

In one of the final scenes, Yondu is shown being cremated while he still has the prototype yaka-controller (mohawk) on his head. In one of the credit-scenes, Kraglin is seen using the same prototype, which would have been destroyed in the "fire".

Character error

Stan Lee's cameo character, an informant for the Watchers explains that in his experiences on Earth, he was a Federal Express employee. This is a direct reference to a past MCU film, Captain America: Civil War. The MCU timeline also places the events of the film in 2016. However, Guardians of the Galaxy Vol. 2 takes place in 2014, just two months after Guardians of the Galaxy. So the Watcher Informant would have no way of telling them of a job he had on Earth if it never happened in the chronological timeline.

However, this error can be argued by saying that he could be referencing to a past event, and not his direct cameo in Civil War. This can only be solved by relying on the possibility that if the Stan Lee cameos in all MCU films are the same person, it would have to be that the Informant would have to continuously switch jobs (he is seen as, for example, a Smithsonian Security Guard in Captain America: The Winter Soldier and a Bartender in Ant-Man) throughout the MCU timeline.

Incorrectly regarded as goofs

The climax occurs in or near Ego's Core, which is repeatedly depicted as having gravity. In the center of a normal planet there is little to no gravity, since the mass of a planet is evenly distributed all around, making gravitational pull equal in all directions. However, Ego mentions that his planet is no larger than the Moon, yet it has a dense atmosphere and normal gravity on the surface. This strongly implies that Ego's planet has artificial gravity, which doesn't have to behave realistically at any depth. Moreover, it is never unambiguously stated that Ego's Core is located in the center of the planet. In fact, Mantis says that the Core is "in the caverns below the surface" (a strange way to describe a center of a planet), and the Guardians, as well as the Sovereign fleet reach the Core too easily for something located in the center of a planet. This suggests that the Core is relatively close to the surface.

Continuity

When Peter Quill is talking to Gamora on Ego, Gamora tosses a radio on the chair. A moment later the radio's position on the chair shifts further to the left, then back again.

Incorrectly regarded as goofs

Before making a series of jumps to get to Ego, Yondu tells Rocket that it's not healthy for a mammalian body to do more than 50 jumps and then they do 700 jumps. After the last jump Groot vomits, even though he's not a mammal. However, Yondu never says that ONLY mammals are susceptible to this "jump sickness". Even if plants are more resilient in this sense, 700 jumps should be enough to make anyone sick.

Incorrectly regarded as goofs

Prior to being killed by Yondu's arrow, the guards push a button to open the cell doors. There is no apparent security code or key. Why couldn't Groot push the button himself to open the door when the guards were away during the night? Just because it seems like there is no security mechanism, doesn't mean there isn't. The button could be equipped with some print scanner, allowing only the authorized personnel to open the door. Or, the guards could have disabled the button before leaving for the night. Regardless, simply getting out of the cell would have done Yondu and Rocket little good. Without the fin they had no chance against dozens of ravagers. Groot, on the other hand, being the ship's new mascot, could walk around freely without raising suspicion.

Incorrectly regarded as goofs

Unlike the iconic Walkman and headphones, the headphones used with the Zune are not original Zune headphones. However with all MP3 players the original owner of the Zune could've broken or swapped out the original headphones for the ones that Quill is using at the time.

Continuity

Peter Quill has a shiny metallic plate-like object behind his right ear, including when he is in casual attire. However, when he is dancing with Gamora on Ego's Planet, he is markedly without it. In all other scenes on the planet, before and after, he is wearing it.

Incorrectly regarded as goofs

When Groot is bringing various items to the cell holding Yondu and Rocket, there are no guards outside of the cell, yet when the fin is being attached to Yondu's head and activated, there are two guards outside the cell. There is no error here. The guards are shown leaving right after putting Yondu and Rocket in the cell and come back to their post only in the morning. We know it's morning, because most of the crew is now awake and at least one person is shaving. It makes perfect sense that this business with the fin took the whole night. Of course, it's highly irresponsible to leave prisoners unattended during the night, but we are talking about a bunch or reckless, drunk pirates lead by an idiot.

Continuity

When Ego is showing Quill how to create the ball of energy, he places Quill's hands with palms facing each other. The camera angle changes and Quill's hands are facing up.

Incorrectly regarded as goofs

Peter calls Rocket a "Trash Panda". This expression was first coined on Reddit in 2014, the year in which the film takes place, even though the Guardians have not had any contact with Earth up to this point. However, Peter could have come up with this expression on his own or perhaps heard it from someone who had some contact with Earth. The appearance of a Zune in the end of the movie does indicate that there is indeed some ongoing connection between Earth and the rest of the Galaxy.

Incorrectly regarded as goofs

The first film establishes that Drax understands things only literally. Yet in this film he shouts "Look out!" to warn of impending danger, and then tells Mantis that she is "beautiful on the inside," referring to her character and not to her internal organs. However, Drax learns a lot about non-literal constructs even during the first film. By the end of it, he even tries to use a metaphor when he kills Korath. Granted, that was a rather pathetic attempt, but he had months since then to perfect his non-literal skills.

Continuity

When Quill tells the High Priestess he doesn't like "anything casual," he starts to clasp his hands together. In the next shot, they are at his sides.

Revealing mistakes

During the ambush scene on Berhert (around 39:11), when Rocket is jumping from one man's shoulder to another, the same rendering of Rocket appears in two consecutive frames in this fast-moving shot.

Continuity

At the beginning of the movie when Meredith Quill is singing "You're a fine girl," her hands abruptly change position during the line "And she works laying whiskey down."

Anachronisms

When Ego's "seedling" behind the Dairy Queen on Earth begins to erupt and cover the planet, many cars are picked up and swept along in the wave of Ego's matter. One of these cars is the 2018 Ford EcoSport, which was not available in 2014.