Is this happening in every design or just ones with longer timelines? I did some quick testing on Mac OS, but I didn't notice anything funny. I'm interested also to hear if anyone else is experiencing this issue.
If you're using anti-virus software, it might help to create an exception for Autodesk Fusion 360 to rule out any chance that Fusion is being "scanned" during normal operations.
Could graphics be a concern? If you go to the Graphics Diagnostic command in the help menu. There's an option to limit all effect to optimize performance. Does enabling this option help?

If you could post an Autodesk Screencast of the issue, it might be helpful as well.
I hope this helps. Let me know if you have any questions.
Thanks,
Nathan Chandler
Principal Specialist