Hey Sam - I thought of something else last night - on ocassion my old lightweight Commander will jam up on me like that when I'm using reloads. It's like one of the empties gets stuck in the chamber and doesn't want to come out. Never happens with factory ammo, only with a reload once in a while.
Whenever that happens to me I just remove the magazine (not always easy), find someplace at the range like one of the shooting benches, er sumptin, where I can use the bench as a stable table, and apply lots of weight against the front part of the slide at the bottom of the barrel bushing, as though I am pushing the slide back. It works for me.
Don't know what causes it - maybe an older piece of brass that just expands to fill the chamber too much, maybe that in combo with a dirty chamber, but when I get the empty out I just toss it.
I'm willing to bet that once you got the brass out she cycled just fine. The mag didn't want to release most likely because of the slide pressure on the top round and the pressure that places on the magazine release.
If you got the empty cleared out she should cycle fine. Try some factory rounds and she should work fine for you.
When you say 'conventional 200 gn swcs' - were those reloads??? Mikey.