It was fairly early on in the room where you need to travel on the horizontal block from right to left. It was the vertical block near the spikes that you had to move up into the hole to pass by.
Hmm... Yeah, I've tried messing around for a bit to see if I could figure out what might cause that, but I'm not getting anything. I've ended up shrinking the platform hitbox slightly though, so if things somehow do manage to get misaligned they should be a little less likely to get stuck because of it.