Can mods cause problems after being removed?

Try deleting the localthumbcache.package file to remove any residual left behind by deleted mods and cc.

I have tried this several times, as well as completely new gane folders ( as I wrote above). I’ve also repaired the game several times, without the issues being resolved. If there’s any residual from the mods it’s not in the game folder ( by game folder I mean the “The Sims 4” folder  created by the game in my documents). That’s why I’m wondering if mods actually can break a save game, even after it’s removed. I’ve never ever experienced anything like that before, but I need to know, in order to maybe determine whether the issues are mod-related or actual game bugs. I’ve found som old bug reports about almost, and some of the same issues, but not recently. 

Yes, they can. Sometimes a "Save As" clears issues up. Sometimes, as when removing a cooking mod, you need to put it back and delete plates and food. Sometimes, as with CC that had a Milestone attached, you need to put the CC back or fix it with another mod (Lumpinou has one). 

Sometimes people actually have multiple folders called "Mods" and don't realize it. This usually is caused by OneDrive but sometimes just by having made copies for some other purpose.

What is a cc with a milestone attatched? How does that happen?

 Save as has cleared nothing, all mods are up to date, and there shouldn’t be any conflicts. Removing all or only some mods doesn’t fix the issue. I’ve tried all the standard stuff being suggested everywhere, I need specifics. Or confirmation of it being caused by mods or the game. 

The issue is basically that one of my sims are missing almost all social interactions towards his spouse. This includes most interactions from game and mods. Only ones left are the non specific that are always present (give gift, tell story etc), as well as settings from the mods (whenever they are installed). The spouse have those interactions though.

There’s also a bug with the spouse, she is a celebrity, and can’t introduce herself to strangers anymore. Only write autographs, hug fans and take selfies. Both sims are celebrities, so this last bug made me suspect that the issue might be with the get fameous dlc.

I have found som bug reports on the last one, but that was years ago. The first one I sort of have found, but they usually mention only romantic interactions missing not absolutely all of them. So that makes me wonder if it’s a bug or possibly mod related. But if removing mods, caches, repairing and creating new game folders doesn’t fix a mod-problem then there’s no real way to find out which mod is causing it, how to fix it, or if it is a bug. Or is there a way?

And no I don’t have two mod folders, and I would for obvious reasons never have onedrive on files that are being changed during gameplay.  It’s hard to understand though, how mods can cause permanent damage to a save file. I don’t really understand how that can happen. Honestly I assumed that it was an EA-bug, still not convinced that it isn’t. But the lack of other people with these issues makes me think that it might be a mod issue as well. 

Growing Together Milestones can be attached to an object they happened with. The most common item for this is playmats, so removing a CC playmat can leave that milestone "orphaned" when the game looks for the object in the catalogue at lot loading. 

For missing interactions, that can be mod-related but isn't always. If testing vanilla leaves it still a problem, you can post here for support: Game Issues. Be sure to tell them that you already tested vanilla.