Hello @David
Given everything you've already tested, this no longer looks like a workbook-specific issue or a typical Excel add-in problem.
The key symptoms are a blank/white worksheet grid and column headers rendered in the wrong position, while Word and PowerPoint display normally. You've also confirmed that it happens with a new blank workbook and persists in Excel Safe Mode.
Since you've already tried graphics-driver updates, display scaling/DPI troubleshooting, resetting Excel settings, Quick Repair, Online Repair, and a cold restart, I wouldn't keep repeating those steps.
One additional test I'd recommend is to temporarily open the laptop normally and disconnect the external monitor completely, rather than running it closed in clamshell mode. This would help determine whether Excel's worksheet rendering is interacting incorrectly with the external display topology/DPI configuration.
I'd also check the exact Excel build under:
File > Account > About Excel
Then install any available Office updates under:
File > Account > Update Options > Update Now
Microsoft notes that recent Excel releases include fixes related to rendering and Freeze Panes behavior, so confirming the exact build is worthwhile.
If the problem remains on the laptop's internal display and you're already on the latest Microsoft 365 build, I agree that this has reached the point where Microsoft Support should investigate it as an Excel rendering issue. You've already eliminated most of the standard client-side causes.
When opening the support case, provide the screenshot, exact Excel version/build, Windows build, GPU/driver version, and mention specifically that:
The issue reproduces in a blank workbook and in Safe Mode after Online Repair, but other Office applications render normally.
That distinction should help prevent support from sending you through the same basic troubleshooting again.
Sharing these references with you:
Microsoft — Excel not responding, hangs, freezes or stops working
Microsoft — Repair an Office application
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