Have you tried to lightly tap the bolt handle up? Be careful as they are sometimes not brazed on very well. It’s most certainly a cocking piece/firing pin/ spring bound issue.
Did you remove the firing pin assembly and clean them prior to the new trigger install?
Have any pictures of the action/bolt from the underside? Can you see the cocking piece through the cutout in the action?
I gave the handle a solid pressure push several times, it does sound like the cocking piece / firing pin is bound. I have not removed the firing pin, don't know how. The rifle is at home but I can see the cocking piece but not being all too familiar with that view, not sure if it looks normal or not.
As previously mentioned, the action area below the stock had lots of build up gunk for old oil that accumulated pretty bad, the trigger was a gunky mess. We cleaned up what we could but not the firing pin/inner bolt. His grandfather used the rifle a lot but never cleaned it, ever that I know of.
