I've done that several times.
Oh, well sorry, I'm not psychic and you didn't mention that in your OP.
Are you sure the graphics that pop in are from a tileset and not another sprite that could be caused by an incorrect image_index assigment or your code switching sprites for a frame when it shouldn't be?
Also try manually clearing all caches, closing GMS2, reopening it, then loading and running your project.
Find the buttons to do this in F
ile > Preferences > General > Paths