I too had this problem, try’d your suggestion and guess what?
IT IS WORKING HURRAY HURRAY HURRAY. @froggy Has been helping me the past couple of days to try and figure it out. I’m so freaking happy that atleast for me this little thing has worked. If your wondering, heaters have no effect on this save bug in my case. Only downside is that it does not fix the saves already broken because of a firepit.
@GrayWren Hope that this works for you too
Edit:
After the original firepit removal i placed it again. As long as it does not have a fire in it there is no problem. The moment its burning the save can’t be loaded. Little side note, ones the firepit was lit it did not stop burning. The citizens did want to trow another log on the fire like you see every night but they just walk away with the log once they visited the firepit.