90% of the SVT problems are solved with the gas adjustment. If you don't have the gas adjusting tool, get one. I went through this learning curve last summer. If you find ammo you like, have, or can readily get, then you don't have much adjusting to do once its set. If you change ammo, you may have more adjusting to do.
I chewed up a few rounds ( ok, lots) when I first shot the thing, but its good now. The brass looks like it gets eaten up, if you're using brass rather than surplus, but it reloads fine as long as there is no damage to the neck. The Russian surplus works and shoots better than the Czeck surplus.
I've only shot 3 different SVT-40s, and they all drive tacks. Very nice, very accurate as far as open sights can be.