Remington 1100 Special field not ejecting

I hate semi auto shotguns. There's a reason I only shoot double barrel or pump action. Semi auto always give me trouble. I do a lot of work on my pistols and rifles without issues, but a family member bought a Remington 1100 Special Field 12 ga that will not eject the shell when fired and asked me to look at it. Just loading a round and ejecting it by hand it works fine. So far I have replaced the O-ring and the piston ring (while making sure the piston ring is oriented the right way), thoroughly cleaned the entire gun including the gas ports and the area in the barrel lug where the o-ring and piston ring seat. I have checked the action spring and it is fine with no hang ups. I can't just try another 1100 barrel because this the Special Field model and the barrel lug is shorter than normal. The extractor has a sharp edge, no debris under it, and good spring tension. I called Remington and they said, "sounds like you have a gas leaking problem...." duh. They also said don't send it back to Remington because this gun is not being produced currently and they do not have parts for it.
Any one have any ideas of what I'm missing here? Thanks!

How did you clean the gas ports?

Oil, a pipe cleaner, a toothpick, then a small piece of wire. The guy at Remington asked if I used a drill bit and I thought he was about to rip me good. He said, "DON"T EVER USE A DRILL BIT!"

Make sure the chamber is CLEAN.

Have you watched it being fired, is the bolt reversing some, just not far enough?

yes, the bolt is coming back, just not enough to eject the shell.

Has it cycled correctly in the past with the same shells?

What ammo?

You shooting lite loads?? Try heavier payload.
Clean/polish the chamber?
Lubed?

https://www.gun-tests.com/ammo/troubleshooting-ejection-failures-on-the-remington-model-1100/

Could be a weak spring. Had one changed on a 20 ga and it cycles without issue now.