One thing I have noticed about my Banish Backcountry that is a significant annoyance is accumulating back pressure when shooting at the range.
When doing load development, the can builds up pressure and I’ll start to get heavy bolt lift and ejector marks. Let the rifle and can cool for longer than what’s usually required and it’s back to shooting normal.
When I take the can off, no pressure.
Also, cans absolutely do get dirty and require cleaning. I didn’t clean mine for about 2000 rounds and chunks of carbon were coming loose and making their way back down bore.
Walk around the woods with a filthy can and bump the can into something (which does happen) and you’ve likely got loose chunks of carbon. Set your rifle down muzzle up and you those carbon chunks are probably in your bore with a loaded round.