Years ago I bought a used 41 for league shooting. Then as my eyes aged I wanted a red dot for it so I bought a used 5-1/2 barrel and had a red dot mounted on it. It worked fine with CCI SV, Aguila SE, Wolf Match Target and Federal 711. Then it started acting up with all of them. I used the old bullseye trick of putting a thin line of oil on the top round and that corrected the problems. For about 3 years, then they started up again. One of the guys at the league suggested I measure the chamber. Sure enough it had grown. The tightest measurement was just over the loosest specified diameter according to the SAAMI specs. That means a new barrel. I wanted to put that off if I could in order to save a few bucks. I tried using grease on the top round instead of oil and that reduced the number of malfunctions but didn't eliminate them. This was the same chassis grease I had been using for general lubrication for years.

I was cleaning it after a match one day and couldn't find my little container of chassis grease so I decided to try Lubriplate 105A which I also had. Worked fine with no problems. Even without oiling or greasing the top round. My problem with that barrel seems to be solved since it ran an entire league without a hitch using the lighter grease.

Just a couple of things for you to check and/or try out in addition to what you have already done.