Hi!
Unfortunately I can report that the issue does not appear to be entirely solved.
I am having exactly the same issue reported in the original post, which is visible in this image:

Thumbnails are scaled to the cell width, but overcome the cell height.
We are currently experiencing this issue on 1 workstation out of 4. Apparently the issue is NOT user specific: a different user on the same workstation exports xls files with the same problem.
The environment is Inventor 2021.3 on Windows10 1903 and excel 2016.
We have tried all suggestions from this forum post, including the excel compatibility setting, but nothing appears to be helping.
We are ready to share any additional detail or information that might help to address this issue.
Massimo Frison
CAD R&D // PDM Admin · Hekuma GmbH