I have done the complete reinstall as suggested, including all the restarts and waiting 5 minutes. I have reimported the lost files and have been working on one folder. I have used DeNoise and this has not led to a new DNG file but instead has resulted in message 'no photos in selected folder' - 1306 photos just disappeared from the view ( the number in the folder still currently shows in left hand panel). 13.1 seems to just randomly corrupt the catalogue.  ... View more

I have reinstalled Lightroom twice and still issues persist with catalog not showing photos in some folders. Rikk you thanked us for our patience - that has run out now. This is creating real stress.  ... View more

Similar issues for me too. Catalog also 'corrupts' in some sessions. Folders show photo count but no photos show in the develop module and then randomly photo count on photos reset to zero. It is a complete mess. Based on this discussion I will revert to v12.  ... View more