ID:1670793
 
BYOND Version:507
Operating System:Windows 8 Pro 64-bit
Web Browser:Chrome 37.0.2062.102
Applies to:DM Language
Status: Open

Issue hasn't been assigned a status value.
test source

Bumping while sliding can cause the mover to stop in a position no longer aligned with tiles, disabling tile movement.

Instructions:
1. Run test game
2. Move around, notice tile movement
3. Click blue tile to "slide" to it
4. Click red tile to "slide" to it, hitting the wall
5. You've been stopped at a non-tile-aligned position, so pixel movement has been enabled.

I would expect to be rounded to a tile position if pixel movement isn't enabled.
atom.step_size isn't meant to be used in non-pixel-movement situations. I don't know how we would easily be able to handle that in a way that would behave the way you want, since it's perfectly valid for step_size to have tile-multiple values in a pixel-movement project.
In response to Lummox JR
Don't get the wrong idea, I would never actually use tile movement. I just saw this odd behavior and decided to report it because apparently I do that now.