The semi/auto switch have been known to give some of the guys issues and have seen several guns run with it removed.
If running the wire stock, check that the notch is square and the spring strong enough on the detent ... not good if goes shut on full. I added a 2nd coaxial spring inside the first on my PS MAC10 in 45ACP, button a little harder to push but the stock stays in position.
I just spray a little breakfree in mine occasionally and maybe wipe stuff down, no real maintenance done. Only parts I've had to replace in the 7 years I've owned it were the extractor and ejector rod. I ran the wire stock on it for a long time, but since I switched to an AR stock it would be hard to go back. I use a RRA Entry fixed stock and find it to be the perfect length.