When Grace is freaking out, she has colored pencils in her hair. These pencils constantly shift positions and disappear/reappear.
When Karen is sitting at her desk, she says "Get out, already," and she has one bottle of nail varnish in her hand, and there are bottles on the desk in front of her. In the next shot she holds about four bottles in her hand, and now the bottles on the desk in front of her are differently positioned.
When Val is folding her towels in the laundry room, she completely folds up a towel as Will enters the room. Then she is seen re-folding the same beige colored towel. Then, though she had picked up the beige one, she is seen setting a dark towel on the stack.
Val says she moved into apartment 15F but the building only has twelve floors.