Re: Endless loading when saving

@TasGreenwood  There could be an issue with your save, or just with the old Sims 4 folder.  Try copying the save to the new folder and see whether you can play it normally and save your progress.  If you can, great, you can add any other content you want to keep to the new folder and pick up where you left off.  Be sure to test again before playing normally if you have any mods or custom content, since those can also be a source of problems.

If your save doesn't work normally in the clean folder, try recovering a backup save:

https://sims4.crinrict.com/eng/2014/09/save-games/#wiederherstellen