I've scoured Nexus and searched this forum to no avail. I find it to be so antagonizing that I'm opting to wait until it's resolved or a work-around is established.
It can be easily recreated by firing any number of rounds from weapons that involve "1-round-at-a-time reloading" that can be interrupted by firing. When you prompt a reload, or it occurs automatically, make sure you are moving. When the weapon has finished fully reloading you will be unable to take any actions for about 1-2 seconds.
The remedy to this problem is to discontinue use to roughly 1/2 of the guns in the game, or stop moving every time you reload.