@Maximum0Dinosaur Whoa! That's a lot of CC! 🙂 I'm glad you were able to get back into your game and yes, hopefully it was just some random glitch. For future reference, I don't think CC is going to cause the issue that you mentioned in your original post. If it happens again and simply restarting the game doesn't work, I would start by testing your game without any mods or CC. If the game works without them, then move to testing mods only. You could create desktop folders, moving mods to one folder and CC to the other. Then you could test your game with mods only and then test with CC only. For both mods and CC, you can then test using the 50/50 method like so...
1. Divide your mods/CC in half (maybe make another folder on your desktop to hold the half you're taking out).
2. Before opening the game with the half you're testing, delete the localthumbcache.package file located in the Documents / Electronic Arts / The Sims 4 folder
3. If the game works with that half, test with the other half. (Again, delete that cache file before opening)
4. Once you know which half is causing the issue, divide those in half and test again (delete the cache file again).
5. Repeat the process until you find the culprit.
Again, I think BuildBuy issues are likely caused by mods, so start with those first. If they're not the culprit, you may need to test the CC and with so many it might take quite a while.