[PLEASE READ] Save Game Corruption

I have had nearly all these issues- the orange exclamation points, the disappearing lots, the default lots, lots not loading, error code 800- all since buying For Rent- in EVERY SAVE. Since lots appear fine from the map it is very hard to detect when - or where- the bug starts, till it starts on lots you are actively using, or near, in live mode or in attempting to load lots.My play style (inc. before I bought For Rent) has been playing in one save with all lots in all worlds (I own all the packs, except some kits), rebuilt with lots downloaded from The Gallery. I have a couple hundred of my own sims since I play rotationally and these sims have interconnected histories. The first save to corrupt was one I had built and played in solely for almost 4 years. I thought that since it was clearly a lot corruption issue I should be careful not to use lots from the earlier corrupted save, when I built a new one, SO I avoided those lots that had been in my library, and downloaded originals from creators on the gallery instead. Still corrupted. In my latest save I played for a couple months before putting any rental units in but then I became aware of corruption (empty lots in Willow Creek and Oasis Springs). I have other issues in Newcrest where the active lot is fine but the lots nearby are empty- but also sometimes are there. In other worlds I am seeing default lots sometimes though all lots load.I want to be able to use Rental units, and I also want to be able to play with the full worlds and lots of sims (though I keep Played Households under 200) that make this game. worthwhile for me. My computer is high end so it is not a computer issue. I play with mods, and have not tried to play without them. Since it is very hard to identify when the bug starts it is hard to test various possibilities.