Game won't save after Build Mode

@missartey  Did you do this test in a clean game folder?  As in, drag your existing folder to the desktop, open the launcher to create a new folder, move your mods and cc over, start a new save, test build mode?  It might well be a bad cc item, or an outdated mod.  Everything could still work separately, but the combination could be causing some kind of conflict.  I wouldn't know where to start looking, but you could ask at NRaas, if you have some of their mods.  The developer and organizers are very good at spotting outdated mods, and also some newer ones that are less than well made.

https://www.nraas.net/community/chatterbox

I suppose it's also possible that your computer is borderline to run TS3 already, and Build/Buy is pushing it over the edge.  (Taking a few minutes to save could be a symptom, or it could just be the result of playing off an HDD.)  If you want me to take a look at your system, please run a dxdiag and attach the results to a post here.

https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/

By the way, you didn't mention it, but leaving on buydebug is a great way to prevent you from being able to save.  I don't know if any of your mods turn it on automatically—I've only heard of a couple turning on testingcheats—but you could try turning it off manually, or else pulling the one mod that's doing it, if you know which one it is.  Since your mods seem to work on their own, this is less likely, but I figured I'd mention it since it's such an easy fix.