Thanks a lot for the offer.
As far as I can tell, it's a bug in bgfx (see one of the issues). Unfortunately, I have to rebuild DLS with the new version of bgfx and I don't know when I'll be able to do it. If I manage to do it, I'll inform you to test it out (if I don't find a Catalina machine in the meantime).
If this isn't the issue, then I'm afraid I cannot debug the app without direct access to a machine.
Sorry for the inconvenience and thanks again for the offer to help.