During a conversation between Natasha and Tom - where he is in the bed and she is standing at a mirror - the sequence is made up of shots of Natalie at the mirror with Tom reflected in it. And shots of Tom on the bed. Tom swaps from one side of the bed to the other between shots. This was obviously done deliberately to keep Tom consistently on the left of the screen but it would have been less obvious if he didn't change his position in relation to the pile of books behind his head.
When Ralphus begins sawing the girl's hand off in the 'dismemberment' scene, the saw is to the inside of the shackle. When the camera view changes, the saw is to the outside of the shackle.
When Sardu is done eating off the girls back, the plate of food is still full when he begins smoking. When he knocks the girl there is nothing on the plate.
When the nipple electrodes attached victim-woman (Jenny Baxter / 'Beaver') is tortured, after Sardu says it will be "excruciating", the left electrode clamp pops off: later after seeing Rufus up the power, and back to her for the last session - both clamps are off / missing.
While Master Sardu calls for Ralphus after being interrupted by Tom, the boom mic with a green windscreen can be seen in the upper left corner of the screen.