Strip it down and inspect the tab located in the upper front edge of the triggerguard housing, where it's supposed to latch into the groove in the receiver underside when it's installed.
IF/when the tab cracks, or breaks completely away, the front of the TG housing will "float" ILO being secured to the receiver.
Feeding issues, including failure of the bolt to completely close, occur because the cartridge feeding mechanism is mounted in the TG housing, and cannot function properly.
The condition is AFAIK un-repairable (the aluminum TG housing cannot be effectively welded or epoxied), and replacement TG housing's are made of un-obtainium.
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