When passing through a static portal, your player sprite is sometimes visible for a split second, right in front of you (maybe for just a single frame). This doesn't happen consistently, so you may need to run through portals many times before seeing it.
First noticed this happening some time after the recent rollback. It also happens in the new level refactor builds. Haven't ever noticed it prior to that.
Have only observed this in the OpenGL renderer. Checked for it in the other renderers, but couldn't get it to happen there. It's possible it's not limited to the GL renderer, though, since it can't be reproduced consistently.
I can provide a test map if needed, but any map with some static portals to run through should work.