Walk is probably a bit of an exaggeration. "Pace back and forth?" When the axle tries to wrap it causes the block to want to rock forward and back on the perch. You can see where it did it on the rear of the perch before it decided to sit forward - the sides are more rusted where the block abraded the metal. I'm surprised you never felt it. When mine started to do that the increased sensation of wrap was really noticeable.

With the gap at the rear grown to what it is, I might start being a little concerned about the block spitting out unexpectedly. It's probably not so well seated on the front of that perch to hold it in if you really stress out the rear end. Be gentle with the stupid pedal til you fix it.