Invisible gun model

I had a bug where my gun model was invisible, but allowed me to continue to fire it. When I tried to reload, the reload animation didn't occur, but the reload still happened. 

What I think happened is the following:

1. I was downed and asking for a revive, holding down the E key.
2. As soon as I revived, I entered the APC vehicle. This may be because I was already holding down the E key, or I pressed it in the same frame as being revived.
3. When I left the APC, my gun model was invisible.
4. The model returned after I switched to my pistol, then back to the primary.

See attached video for details. I was playing as Engineer with the MP7.