No problems with my 3.5" gun now. When it was new, it didn't like 1 1/8oz loads, and breaking it in took care of that. The only malfunctions I have had is due to an excessively dirty gas piston, but that was a few years worth of grime.
I never cleaned the action spring in the buttstock, but that can cause some of the problems a few of you are facing. The only time I took the spring out was to replace it with a Sure Cycle, and I haven't cleaned the Sure Cycle since I installed it.
When I feel like cleaning mine (couple of times a season, probably), I wipe everything down with CLP or RemOil, and use brake cleaner on the gas piston. If the powder spots on the mag tube are tough to get off, I use Hoppe's and a brush. No lube, as I after I put on the CLP, I wipe it off. This leaves a very, very light film behind, and is all you need. In the extreme cold, I have had no problems, but don't have any problems shooting it dry as well, as I did that for years.