I saw something similar during a qual at my last agency.

Officer had a Glock 22 in a kydex holster. He was wearing one of the raid jackets with the plastic knob thingies suspended from either side of the jacket.

One of the knob thingies plopped over the top of his holster while he was shooting.

He reloaded and then reholstered while the knob went inside his trigger guard. BANG! He had an awful looking scar on his backside.

Another reason I've no use for striker fired plastic pistols. Regards 18DAI.