@imahobbit4real It's possible that something else (not custom content) in your user data folder is corrupted. It's also possible, although it would be surprising, that a certain cc item is causing problems only some of the time your game loads. But in either case, it's probably best to start with a clean user data folder, test your cc there, and then move your saves and other content to that folder when you're done.
Move your entire Sims 4 folder out of Documents\Electronic Arts and onto your desktop, and when you launch the game, a clean folder will spawn with no content. Move the 366 cc items that worked before into the new folder, create some sims (no need to spend much time on them, since this is just for testing), assign some of that cc, save, quit, and reload a couple of times to see whether it all still works. If it does, you can add half the newer cc items and test them too; be sure to add those to sims, so you know whether those items work. If they do, add half the rest and test again.
When a batch of cc doesn't work, whether it's the original 366 items or the new 16, you'll need to split the batch and test until you find the problem file(s). Since it sounds like the game only goes to a white screen some of the time, be sure to test multiple times. Even with as many cc files as you have, it shouldn't take too long to sort through all of it if you split each nonworking group in half.
