(at around 8 mins) After hitting the goat in the forest, the blood on the van disappears in one shot.
(at around 7 mins) After one of them hits the goat with a pipe, blood gets splattered on his face. But in the next shot the arrangement on blood on his face is different.
The constant bird sounds in the background throughout the film frequently include the very obvious Red-Winged Blackbird which is not found in Europe, never mind Ireland, where the film is set.
Liberty Caps which in the movie occur in a forest/wood are not found there in real life. They're only found on fields. They are especially abundant in cow pastures and in freshly fertilized fields when cow manure is used as the fertilizer base. Deliscious Oyster mushrooms grow in the environment that is shown for the Liberty cap aka "shrooms". They like downed decaying logs and the sides of trees covered in moss. Grow in Spring, Summer and Fall in moist areas, like a rain forest region.