I guess this can go here, as I've run into a problem with the Dboys HK416. So, I was about to clean up the stock greases inside the mechbox (gun belongs to a friend of mine) but I hassled a bit with the gun and came up with a problem concerning the bolt catch and its moving parts. While moving the black part on the right side of the GB, a spring popped out (the piece is marked with a red ring, first photo) and I have no idea how to get the spring back in place. Only advice I got from Finnish airsoft-forums was to get rid of the whole bolt catch because it's easy to break in use.
Here's a