I don't know how to reproduce it properly but:

Shoot with a Weapon of your choice and hold the trigger when it is reloading. Shoot again and stop holding the mouse button. The weapon will reload even if your magazine is nearly full.

Same problem seems to happen, when your Stamina is empty. If your Stamina is empty your gun is reloading (maybe works as designed?). When you shoot afterwards, and you release the trigger the gun will be reloading again.

It is really annoying.

Other Bug which comes with it. You can switch your weapon to the next one in your QB, without releasing the trigger and you won't realize a break while shooting.
I think shooting should stop, while you switch your weapon.
So at the moment it is possible to have like 5 Ionic shotgun pistols and fire them nearly at once. Or you have two AK47s and have a 60shot magazine when you are able to switch the weapon at the right time.