Can be anything, from characters not using objects they have on them, to physics not being realistic, or a very big plot hole.
As an example, one of my friends told me that his pet peeve is that in a lot of sci-fi movies, when spaceships run out of fuel, they stop moving, while inertia and lack of atmosphere should keep them in motion.
POV when using binoculars has two circles, which isn’t how it looks when you actually use them. It should be one circle.
Camera footage that’s played back in movies as part of the plot always has the recording icon, time code, etc burnt into the footage, which should really only be visible on the camera monitor while recording, not during playback and especially not on another device.
old VHS cam-corders did burn some of that info onto the tape.
Yeah, but it’s almost never a VHS camera in the movies, and now often a smartphone video.