I had the same problem - only visible with MS Excel and no other programs. Areas that are blacked out would shift on scrolling but never go away unless window was reduced in size and zoomed in. This made it impossible to work on large spreadsheets.
My hardware includes Dell XPS15 9550 with TB15 thunderbolt 3 dock and 34" dell 4k monitor. Right from first install the problem occurred (see screenshot below) and Microsoft help was no help at all - no suggestions after an hour on chat with remote desktop access with the help dept. Very frustrating!
I updated all Dell drivers and video card drivers with no improvement. Tried reinstalling Office 365 twice with no improvement.
Then I reinstalled Office 2016 Professional Plus and the problem disappeared.
Subsequently worked with Office 365 Std as well. I can only conclude it must have been some form of corrupted file during the download/install process? Very odd and took a lot of time to find the solution.