When Jessica is painting and writing on the wall and confronted by Taylor and Gloria, there is a green mark of paint on her forehead that disappears and reappears in between shots.
When Jess and Tom are having a conversation in the bathroom before he leaves, there are obvious reverse shots as the words on his shirt are mirrored, before then reverting to normal in the next shot.
At 15:00 when Taylor takes a selfie, the camera feed is shown on the phone live. When she snaps the photo, it changes to the picture taken, which is nothing like what was fed from the camera.
When they use the paint to cover the door, the paint is freshly mixed even though it's been sitting in a basement for several years.