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Yes, it is supposed to stay back if you push on the BOTTOM of the Bolt Catch, while holding the bolt to the rear. Then return the charging handle gently to the forward pos'n., until it locks in place.
Then, you press on the TOP, and it will release the bolt.
Unload the other mag, and try it on both tonight. Don't touch the button, until you want to release the bolt. The bolt SHOULD lock back on a empty (serviceable) mag.
As far as the bolt not locking and back bolt flying forward, well it could be that your mag release needs to be tightened up.
This might cause your mag not to seat (not locked in tighly).
It's very simple to tighten, but first let's see what happens tonight.
Look on the bottom to see the manufacturer. They are 30's?
Try going here, for more reading:old.ar15.com/
The articles are easier to get to. Read the owner's manual cover to cover.