There’s a lot of little issues that might be contributing. The obvious things like make sure you are using a lightmass importance volume, baking on production. What does the model look like? Are there open edges? Posting the OBJ file might help with trouble shooting as well. Probably should post a Lighting Only view as well, textures can mask the issues.
That is horrible advise. Waste of memory and time to use resolutions like that on assets that don’t need it.