The layout quality of 3D scenes degrades for any scene that is not on top of the layout's table of contents. If I switch the order of the two scenes shown below, only the topmost scene in the TOC will draw with high quality. I'm using ArcGIS Pro v.2.9.3. Has anyone solved this problem?
I assume from the picture that this is Integrated Mesh data? Can you provide the details and report it as a bug to https://support.esri.com/en/report-bug so it has a paper trail for teams to investigate.
FYI we found the root cause and were able to resolve it for the next release (3.0). I will link your reported bug to the development issue when it comes in so that it can be properly processed as resolved.