SQUEEEEE! I'm so very happy the problem has been discovered!
And that answers the question of why my game was running so smoothly -- I hadn't yet installed any store stuff, so the tree wasn't in my game. And the mermaid testing game with LL installed, which has the tree, was still a new game, so the problem didn't have time to rear its head.
I've been playing my old DV save game, with all store stuff installed as of DV, and that one has, so far, played perfectly. It has the tree installed, but again, I have not played it long enough for the errors to mount.
I do have a question: I have read that the alarms will follow from one save to the next. I get that. But, will they piggyback on lots saved out of a corrupt game? Or sims?
EDIT: Cyron, when you uninstalled the tree the first time, did it also uninstall LL?