I don’t entirely understand the “pump shotgun” thing. I have never had my 1187 fail to chamber a second round.
Nor I.
Unless it was with low brass field loads...and I find them next to useless, anyway.
I have an early 1100 and a later 1187.
Neither have failed to chamber, except with low brass.
And that's just about every 8th or 10th round.
No idea as to why, other than carbon buildup perhaps or just crappy field loads.
Now, if I shoot low brass field loads, I use my 870.
It's simply a matter of mechanical reliability.
The 11 series Remington are known for that peculiarity with low brass...but then, why the hell would anyone be in bear country with low brass field loads, unless you were after grouse or fool hens...and then I'd damn well have a BFR backup.