Drop shadow reverting to default settings if I move/zoom canvas or zoom in/out?

I have a rectangle with a subtle drop-shadow effect applied, and anytime I try to move the canvas (or the rectangle itself) the drop-shadow reverts to the default settings or dissapears completely? The shadow becomes black, 75% opacity etc, and I'm forced to re-adjust it anytime I want to move the rectangle or alt+drag around the canvas.  I attached some gifs to show what happens (one when the shadow dissapears, the other when it gets darker) 

My Fx options are always how I left them (light gray, 60 opacity etc.) sometimes I can just click okay and the shadow goes back to normal - other times I have to change something (like check/uncheck a box) for the changes to be applied on screen. 

When I export to pdf the shadow matches my applied settings - even though on screen while exporting it's super dark.

I read a few posts about drop-shadows and tried changing these settings but the issue still happens. 

view > overprint preview

transparency blend space > RGB 

Any insight would be much appreciated!