S&T PPSh-41 upgrade troubles

[Sasha]

Hey, guys.

So, I bought an S&T PPSh-41 recently and, having read/watched several reviews that claimed that the cylinder/piston assembly was crap, decided to upgrade them. Boy was that a bad idea; this is not an easy gun to work with.

After about 10 hours of work, I managed to get everything in properly, or so I thought. When I put the mechbox back together, the gun will cycle fine on automatic, but when fired on semiautomatic, or after releasing the anti-reversal latch (which can be done through an external de-cocking lever), the gears will push the piston partway back (varies from several millimeters to all the way) and then start spinning out. I'm kinda stuck here. I've tried moving shims around to stabilize the gears, but without much success. Anyone have any idea what might cause something like this?

For reference, the otherwise stock gearbox has been upgraded with the following parts:
http://airsoftdepot.ca/catalog/produ...oducts_id=2558 (does not include piston)
http://www.torontoairsoft.com/SHS-15...on_p_1313.html
http://www.torontoairsoft.com/Elemen...ing_p_658.html

The stock internals look like this: https://www.youtube.com/watch?v=dk6Kipe6IY4

I'll post pictures of the gearbox in its current condition later when I have it apart again, I'm not keen on looking at it now lol.

Thanks!

Edit: Never mind, I figured out this particular issue on my own.