@WastedBliss Sorry I didn't get back to you sooner. I don't recognize the error, and I looked around a bit for something similar, and I was going to ask around... but then I just forgot.
It's probably related to mods or custom content though, maybe something you used in the house. One test you can try is loading the save in a clean game folder. Move your entire Sims 4 folder out of Documents\Electronic Arts and onto your desktop, launch the game to create a new folder, redo your graphics settings if you want, and quit. Then go into the Saves folder inside the Sims 4 folder that you moved, copy your save, and paste it into Saves in the new TS4 folder. (Copy instead of dragging and dropping so that you can mess around with the new copy and still have the original as backup.)
If the household loads, great; that means the issue is something inside the old game folder. Quit without saving, move some of your mods/cc to the new folder, and test again. Any batch you move over that prevents the save from loading properly needs to be split and tested again until you find the problem file(s). Once you've sorted through everything, you can move over any other saves you have, plus the contents of Tray, which contains your saved households and builds.
If the save doesn't load even in a clean folder with no mods or cc present, try playing a different household first, for at least a couple of sim-hours. If that doesn't work either, try loading a backup save. Use the manual method described here:
https://sims4.crinrict.com/eng/2014/09/save-games/#wiederherstellen