kuligs2 New discovery. It doesn't happen until after the scene containing the tilemap is saved. New pictures don't matter nor creating a new project. I'm not sure if I should be worried about proceeding with the project until this is fixed. (I'm gonna see if it happens on earlier versions in the mean time, keep ya'all updated)
EDIT: It appears to be something about 4.6 in general as the problem only stopped once I reached 4.5.2 which does not have this problem.