I have been cleaning up my collections. Reordering them by pack, adding CC addons, and most importantly, removing the lot type specification of the collections that have them (ticking both comm and res, adding the missing items between the two collections to one of them, and deleting the other) for simple ease of adding, reordering, and removing items from collections regardless of where I am. For every other collection this worked out fine, but after doing this, the base game collections went invisible. They are there, and I can organize their order from the collection manager window, but they do not show up in the list for comm or res lots. Is this a known problem, and if so, is there anything I can do short of deleting and recreating them?

Sounds like a useful project. I don't know what the trouble is, but if you need to get them back, you could just copy them from the install files. I have UC; mine are in TSData/Res/UserData/Collections for each EP.

They are still there though. they are just invisible. As in not appearing in catelog. But from the organize collections panel they can be seen and reorganized. I guess I could try to replace their files and try again.... But until I know the problem, how can I stop it frlm happening again?