Same here since ?ever? I don’t use the full preview in lighttable mode, so I don’t care.
Yes, I have it enabled, but that does not change anything.
Lighttable shows preview images from cache, but I don’t know how resolution and quality of this images are controlled.
In darktablerc there is an entry
database_cache_quality=89
In darktableconfig.xml.in it says:
short: JPEG quality of on-disk thumbnails
longdescription: affects only the thumbnail cache used for quick startup
What happens if you set a higher value here?