Clarification:
This doesn’t happen every time I pan, just like once or twice a minute or so. In those moments it’s not just pan but also mouse zooming. Likely any input, just pan and zoom make it most apparent. The rhino viewport simply gets stuck for about one second, then catches up.
I never had this before and it doesn’t appear to be related to file saving. I can’t say for sure but I think it is a rhino display issue.