Horizontal scroll in Excel locks up the Vertical Scroll.
1. Vertical scroll works as expected
2. Use horizontal scroll
3. Vertical scroll is now locked out and now movement.

To reset:
1. Click either vert or horz scroll bar. Vertical and horz scroll work again until next horz scroll.

To fix:
Set Excel to run as admin. This has a secondary side effect that it breaks power query but does fix the scroll issue. I cannot leave this way because of the power query issue:

Excel:
Microsoft® Excel® for Microsoft 365 MSO (Version 2111 Build 16.0.14701.20254) 64-bit
OS:
Edition Windows 10 Pro
Version 21H1
Installed on ‎9/‎10/‎2021
OS build 19043.1415
Experience Windows Feature Experience Pack 120.2212.3920.0