When Beth is being beaten by Jake at the start of the film she is thrown into a mirror which shatters completely. Later when the children are cleaning up the mess the mirror is back on the wall with only a few cracks.
The swallow tattoo on Rena Owen's breast disappears between shots.
When Beth and friend are out looking for Grace in the car, its raining outside. When they go to a front shot of the car its not raining.
During the first party (when Jake forcibly ejects a "wanker" male guest), there is a continuity error between when we first see Jake angrily coming at the guest (from the inside, in the kitchen) and the shot when we see the guest ejected (from the exterior of the house). The error is that from the inside we see one exit from the home (just to the left of the kitchen), and from the outside we see the guest being ejected from somewhere entirely different (looks like from the opposite end of the home entirely, because you can't even see the kitchen windows which look out onto the backyard).
When the scene of the guy singing karaoke in the bar right before Jake and Dooley walk in, the camera scans and you see an old guy among the people watching the singer and moving to the music, then you see the same old guy sitting at the bar when Jake and Dooley are discussing the guy who just beat up three other guys. He moved from one scene to the next within seconds.
When Beth sees Grace hanging from the tree, there is nothing under Grace for her to have stood on to tie herself up there, and the tree is too high for her to have climbed.