This has been in since day 1 and I've tried to find a tracker for it but no one has put one back.
I have a video of this I will upload tonight and attach showing I couldn't throw a grenade. This video is from last build, but I encountered this issue within 20 minutes of playing on the current build as well.
I think this issue is caused by desync, the player side shows you throwing it doesn't leave your hands and it then stuck out of sync with the server.
The only way I have been able to resolve the issue was by random chance of falling off of a cliff on to another rock which the switch in animation allowed the grenade to be tossed.