@TURBODRIVER
Hmm. Thanks for explaining that. So I've been scouring the files for something that could be related to what you're saying. So far, not really having any luck.
If it helps explain what I'm working with, the custom needs that I talked about are two needs "Magical Connection" and "Alignment" that are added via a trait and work like the special Vampire or PlantSim needs, where they overwrite some of the default needs. Those are the only reference to a statistic I can find in my files, or think of, that would be having an issue. Bizarrely though, in most ways, they are exactly like the Vampire or PlantSim needs, so it's not as though there's a huge difference.
The only reference to statistics or states I've been able to find that has anything to do with my mod (apart from the two needs I just mentioned) is abilities to do with starting a fire or putting out a fire, and the fact that I added an interaction to the blob of clay (which has some states). But I checked those files carefully and am seeing no changes between how they work on Maxis's end pre-patch and how they work now, so I can't see any reason they'd be related.
In my testing, the center of the issue seems to come back to the custom needs.
Here's another trip into bizarre land: I have a "corrupted" save that I've been using to test things, to see if I can "uncorrupt" it reliably. So far, the only way to make it loadable is to not have any Sorcerers in it with the custom needs. In this special save...
If I contrive a situation where there's a Sorcerer with only one of the custom needs (doesn't matter which one, I tested both) no error. If I give them both custom needs at the same time, the error returns.
The only way I'm seeing at the moment that this can make any sense at all is if it's tied to the fact that casting a spell usually affects both needs at the same time. Say I cast a "Dark" spell called Bizarro Land (not a real spell, just go with it :P), it does -5 Magical Connection and -10 Alignment. Or if it's Light, it'd do -5 Magical Connection and +10 Alignment. I can't imagine why corruption would occur in that, but it's the only thing I can think of at the moment where the game could theoretically get caught on trying to modify both values at the same time and the data gets corrupted somehow? Then it gets saved that way, which could maybe explain why the save is only "uncorrupted" if it doesn't contain a sim that has both of those custom needs.
But I mean, I think that's like need-to-go-to-the-chiropractor levels of reaching for an explanation. And it'd have to be some kind of corruption across the whole save, not just tied to a specific sim, cause with the testing I've done, it's if any sim in the corrupted save is given both custom needs at the same time that the issue returns, not only the ones who had the custom needs previously.
