Revealing mistake: When Belle exits her house, the reflection on the window by the door shows a rectangular flat roofed building, nothing to do with the old gable roof we see in further shoots. In the making-of we are revealed that the prop building is in fact rectangular and flat, with a green screen on top to allow for the CGI.
Revealing mistake: After Rey lifts the rocks away from the back exit of the bunker, you can see C3P0 briefly as he bumps into the rock in front of him while exiting the cave, and the rock moves slightly. Also, the rocks that fell over the exit don't match the surrounding terrain at all while piled up as they are smooth like river rocks, but when we see them lifted up by Rey in the subsequent scene, they are rougher and look nothing like they did before (as well as being pretty lousy CGI). (02:16:47)
Revealing mistake: During the underwater scenes the light appears from below and above but it's underground and should be pitch black, suggesting studio lighting being used.
Revealing mistake: When The Ray lands on the ground regrouping with the other Freedom Fighters, there is a bridge behind him with many civilians walking in the background. The animators took an obvious shortcut here as the civilians in the background just consist of the sprites of about 5-7 different people just repeated over and over again all in their same poses on each copy as they move. One especially noticeable one is a kid walking in an olive gray shirt with his arms up right next to himself over and over again. (00:01:45)