Thanks for reaching out with the details. I'd love to help you figure this out.
Could you please share the version of Lightroom Classic & the macOS you are working on? Does this happen after a series of steps or tasks or from the launch?
If you are working on macOS 12.3 & above, please try the following steps.
If this does not help, the issue could be related to this specific catalog which could potentially be damaged. We can bring everything from an existing & probably damaged catalog to a new catalog.
Copy the primary catalog in question and place it on your computer's desktop.
- Go to File > New Catalog or press the OPT (macOS) when launching Lightroom Classic.
- Choose the option to create a new catalog and create a new one on the internal drive.
- In the new catalog, head to File > Import from Another Catalog, as shown below.
Proceed with merging the (potentially) corrupted catalog into the newly made, internal storage-based catalog.
For more help via video-based steps, check here. See Merging individual catalogs into a master catalog.
Let us know how it goes from here,