I wanted to add to this topic with an example as I just experienced this!

Aspen with 80 SLVL (has had three interactions so she has 30 from that)


If I add this Blue Safe (the one on C3, doesn't matter where I put it), the SLVL goes down by 3.


Her SLVL does go back to 80 if I remove the C3 safe. I also tried removing other items to see if they would cause her SLVL to go up, but it all resulted in it going down. Adding additional items that aren't that safe also cause the SLVL to go down. So maybe there is an unseen, intentional item limit or this isn't intended?

Maybe this is a house-specific bug? I'm in the starter hut and I don't experience any of this, and everyone here seems to have bigger homes, which is why I think that it might be house-specific. (+ Aleanore mentioned the bug happening after moving into a new home)

Just wanted to put in my two cents that I've noticed this issue as well!

This is possible! Especially if caused because we're going over a certain number of decorations, the starter house may not be able to hold that many items, or it's an issue specifically with the Woodland Bungalow. Maybe someone with a Designer Two Story could try to jam pack one of the inside rooms with decorations to see if it's also a problem in that house. 0: Since everyone so far who has experienced this are all in the same type of house.

Only the 20 most rare objects count towards the SLVL.
I looked into this and there seem to be a problem with how rarity is sorted. It seems like until now the objects with the highest rarity (so the most unrare ones) were selected fist. I reversed that now which should change behaviour!