OK, swapped out glass with my P-B, same problem. Both glasses fit fine in P-B. P-B has a plastic rear channel and HS has a stainless steel one.
Found the screws that hold the rear channel in, they were secure. I tried to loosen and adjust the channel down, but no change.
The glass is just barely catching, like 1/32 or less. P-B and HS both got new glass about 2 years ago. I still had old original glass, so I tried it, went right in. It touched the lower channel guide as it slid in, but still went in smoothly.
The glass was purchased from BAA, turns out original glass has a slight bevel on the edge, new glass does not. That bevel allows it to slide into the channel, where as the square edge glass catches and the stainless steel channel has zero give.
Not sure where I'm going from here, old glass is all scratched up, new one won't go in.
I believe the new glass has been catching slightly since installation, but never caught bad enough to not go in. I still don't know why that has changed.