Hmm. Interesting turn of events. So I tried another idea for trying to narrow down the problem. Reasoned that if it only comes up when the two custom needs are added, maybe it's actually something to do with the interactions (because some of them have global tests pertaining to the needs being at certain values, that sort of thing).
I tried just removing the scripts that inject the interactions. In theory, this shouldn't cause any problems... the interactions just won't show up anywhere. Instead, it did something a little different on a corrupted save. Instead of only giving the error message for the usual one sim ID, it gave it for 3 different sim IDs (there's a total of five sims in this corrupted save, three of which, if I recall correctly, have the base Sorcerer Trait related to the mod, though only two are adults with the two custom needs... one is a child).
I would bet that the 3 sims it's referencing are the Sorcerers. Still doesn't pinpoint the issue, but it does play into the theory that it's something tied to the scripts and interactions.
EDIT: Lol. So I interpreted this partly right. The number of sim ID errors is probably corresponding to the number of sims with the base Sorcerer Trait from the mod, in the save file. But it was giving 3 sim ID errors on this particular file, regardless of whether the scripts are installed. I got confused because I'd been testing on a file with only one Sorcerer in it and got used to seeing the one error message in a lastexception file.
