I have experienced this today:
Mosin pristine
compensator pristine
long range scope badly damaged
when in 1st person the aim will jump along the x-axis OR the y-axis when completely zommed in (RMB). it is NOT swaying, the aim JUMPS. First it was jumping along the y-axis, half an hour later along the x-axis. my character was not breathing heavy, was prone, no broken limbs, stress, etc.
zooming in only half the way (using + and - on numkeys) sort of fixes this because the jumping seems to only start at a certain point.