When I first started many years ago, I was told always to save (save as) from the plan view, never the 3D window - unless you want to save a particular 3D type.
So maybe try again from the plan.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10