Other players have reported the same behavior with this type of weapons/ reload type

After the reload animation it sometimes occur that you cant do any actions (shooting, vats, pipboy, change weapon) for a few seconds.
faster reload (lvl2 perk) doesnt effect this, it happens with or without.

Has somebody fixed this yet? Or any ideas whats the origin of this "lag"

It happens when you reload while moving.

I'm not sure it's lag as much as it's the "jammed gun" animation not playing while in motion. I could be wrong though.

Either way, it's annoying and yet another issue needing to be patched

It's quite annoying in the heat of combat when you're hammering on the Pip-Boy key and meanwhile your character doesn't seem to be reloading or anything, and you're getting wasted by enemies.