It is very slight (less than 1 pixel) but enough to offset the player by 1 pixel.
It has always been like this. Platformer object floats slightly over the floor.
There are two workarounds:
1. Attach a separate invisible sprite used specifically as a collision mask. It could be 2px larger than your character, for example.
2. Use "Is overlapping at offset" condition with 1-2 px offset, to check if the character is touching a solid object.