During the water park scene, the body builder is seen to remove his sun glasses and toss them on the lounge chair. In the next shot, they are back on his face. In the following shot, they are back on the lounge chair where they landed when he tossed them down.
When Rob Schneider kicks David Spade in the groin on the second kick he falls over in pain, but the next scene he is standing up with no pain.
During the first "arrow roulette" scene, David Spade falls face-first into a pile of poop and is completely covered. In the next scene, he is completely clean.
The number 55 on the back of Eric's jersey changes width and style multiple times during the basketball game at the end.
The wives are shown sewing "uniforms" for the big basketball game. During the game, the men wear t-shirts with the logo of the water park, and a logo of the t-shirt company clearly visible on them - obviously not made for them by their wives. The women arrive in newspaper cheerleader costumes - also not what they were sewing.
No water park (indoor or outdoor) would have a zip line as it's dangerous and it could lead to serious injury or death.
The injured bird in the movie is an Eurasian Collared Dove, but when they set it free we can hear singing of a canary bird or a similar small type of bird.
When everybody's entering the lake house for the first time, after Rob says "Welcome back to 1978," and the camera shows all of the characters, a crew member can be seen running past one of the windows on the left.
Throughout the movie, Lenny is trying to hide from the group that Rita is their employee, but when she tries to serve him coffee after the funeral it turns out he texted her asking her to bring him coffee. It doesn't make sense for him to ask her to do anything in front of the people he's trying to hide her role from.
For the first round of Arrow Roulette, the implied idea being to shoot an arrow straight up at 90 degrees so it lands where they're standing, Lenny shoots at a pronounced angle, 75 degrees or less. Without a strong wind, which is clearly not present, the arrow would land hundreds of feet away, posing no danger.
The muscled pool hunk states he is from "Saskatchetoon", seeming to mean Saskatoon, a city in the western part of Canada. However, he speaks in a strong Canadian French accent, meaning he is from Quebec, in the Eastern part of Canada.
When the muscled pool hunk comes over to talk to the wives, he proudly declares he's from Saskatchetoon. This is an amalgamation of the place name Saskatoon, Saskatchewan, a large city in the western part of Canada. If he was truly from Saskatoon he would know the correct name and how to pronounce it.