I have experienced this particular bug maybe 3 times in a 7 year period of playing. The last time I experienced this was around 4-5 months ago. Lasted a few days, then goes away. Last night Tuesday 5/29/2018 , it was happening again.   It only happens when enabling Marksman mode on opposition, does not happen when zooming in on objects or NPC's.   So it's a constant batte trying to zoom in, or maintain Zoom, as I am immediately toggled out of zoom.