Not sure why you compare 50rd to 20rd, stock mags are 35rd. But hey ??

The real test is how many shots can you get from one gas fill?
Aye the stock bolt deforms on the hammer reset, but only so far, it work hardens. In all honesty TM could have put a steel chip there.
Non the less the stock bolt works perfectly for 10s of thousands of rounds.
I do like a lighter bolt, it has many benefits.
But the rollers on the G&P are unnecessary as the bolt centrally locates to the buffer part ‘A’.
And with the buffer spring/tube/assembly lightly coated with Moly grease it works very slickly.
RE your problem; using the stock TM mag as a pattern, line the mag catch detent up with the ProWin mag, and look for discrepancies in the height of the upper plate, feed lips and gas route.
You will most likely have to file/sand some shit down.