I’ve had similar issues with front rails being loose. It seems like most designs just have a bit too much clearance. Side to side play can be fixed by shimming with pieces of metal from soda cans. One layer shoved between the rail and frame on either side of the rail. For the rocking I’ve reduced that by melting small areas of the frame plastic with a hot nail to fill in the gap between the front and/or back of the rail and the frame. Like staking an AR-15 castle nut or bolt carrier if you’re familiar.
As far as the pins walking, I’ve ended up using a size smaller drill bit (whatever imperial size is just under 3mm) for cleaning up frame holes to keep them from getting too big. Then dry fitting the pins and drilling the holes a bit more until they fit snugly. You could also stake the front rail pin in using a hot nail like the rail. Or a dab of super glue.
I’ve only used Aves rails so I’m not sure how others compare. But the front and rear rails, and the locking block, from Aves have all worked fine for me. Another option could be bedding the front rail with epoxy or something.