What hell, pay attention
You are "slapping" the charging handle from its locked open position when youre charging the gun, right?I have been thinking about this (I'm at work) and I think she is just not going all the way into battery.
Charging that rifle requires considerable effort, not sure if the recoil spring is the culprit. So now I'm going to take apart and polish every working surface in the bolt group with polishing wheels and jeweler's compound.
If you are easing the bolt forward to chamber the round, you will get the exact mafunction you are describing.
The way you charge the HK's is to either slap the charging handle from lock, or pull the charging handle fully rearward, and release.
Anything else, and you will likely get that malfunction.