That sounds like it could belong in Sigblasters malfunction thread.Why? Well, let me tell you.
Basic Training. My first day on the range. My first round. I inserted the magazine, pulled the charging handle to the rear and released it, took the weapon off safe, took aim and fired.
The charging handle did not lock and it slid back (not with the full force of the bolt carrier) justt slowly tapped me very lightly in my cheek just below my eye.
I developed in that one incident a years long flinch that kept me a marksman for years.
I can see why that would give you a flinch.
It doesn’t take much to hold it, as proven by the light springs on my Strike Industries, but it does take something. Makes me want to do some experimenting and make a video.