I’m still waiting after nearly two years as to what’s causing it. I didn’t feel it necessary to put in yet another bug report. It goes way back and gets worse or better with patches or hotfixes. (Refer to link below) Yes, it is a serious issue as on a few occasions like now, I can’t play the game long without it becoming too bothersome.
It never got fixed for some of us. I’m likely one of the few that’s hung in there this long waiting for it to be taken care of and thought it finally was with the mounts update.