I have found what seems like a possible rounding error with collision detection on flipped tiles.
Basically, tiles that are flipped can sometimes collide slightly outside of their grid space. In the example project the player object changes color when standing on a collision tile. However some of the flipped tiles (left facing arrow) are colliding when the object is adjacent:
It seems to be more likely to happen when you are farther away from 0,0. Here’s the project: