Sims forget already existing relationships

I have been noticing this happen more and more recently, including forgetting their own family members with whom they had good relationships. I am not sure if this is the reason but it does seem to be occur more frequently when swapping between different households? I had sims completely forget their roommates when i left to play in a different household. All of my sims knew one sim who had died and suddenly none of them, including her siblings and uncle, had ever met her before but she's still on their family tree. 

On PC, never had any mods in this save, all my packs disabled except Get to Work and most kits.

Every so often the members of my family will have their relationship progress culled, sometimes even mid-conversation. This result in parents suddenly not knowing their toddlers/children/teens and siblings forgetting about each other despite living in the same household and interacting frequently. It's quite annoying to have a child with maxed out friendship with their father bragging about her grades one second and then having to make friendly introductions the next. They still seems to keep their family tree relationships though, so they are still father and daughter etc, they just act like they never met. 

So far I've caught it happening 4-5 times in the same save/household but between different sims and at different life stages. If it makes a difference the household consists a human mother, an alien father, their 3 half-alien kids and another full alien (step/)daughter because the father got abducted on their wedding night. The mother has never been involved in the culled relationships to this point, but everyone else has.

Hi new in this thread, my game has the same issue. Currently playing R&L - my Sim met Fia and have a negative relationship. after logging in the second day, Fia disappeared from my Sim's contact book. Before R&L, same issued noticed with Enchanted pack as well.

My sims keep losing their relationships with everyone including sims outside of the household and ones on the family tree. I have to reintroduce them every time they interact with one another and all of their sentiments are reset too because of it. I’ve tried the cheats but their relationships get wiped as soon as they leave the lot. 

Hello, I have the same problem with my game. I play without mods or custom content. I play with several households in my game (the household I'm currently playing is in my played households, and the others are in the unplayed households in the household manager until I return to them, as I only enable the automatic age adjustment option for played households). I usually spend one or two Sims weeks with a household and then switch to another. When I return to a previously played household, I find that all the relationships have disappeared! This includes landlords with their tenants (with high friendship levels), teenagers (with their high school friends), and sometimes even romantic relationships within a couple! Is there anything that can be done to prevent the game from deleting friendship data after 15 Sims days?

I am trying to set up a wedding and want the in-laws there, I am just switching families so they will be wearing appropriate clothing and when I got back to my main sim he had forgotten all the other in-laws and even his ring bearer. So I reintroduced them all again and when it was time for the wedding he had forgotten some of them again even though they had an engagement party and a bachelor party and a wedding rehearsal dinner. I finally had the wedding without the officiant , best man and the ring bearer. It was so frustrating.  I wish we could invite households like in past sim games. Why can't all the in-laws just be included when trying to set up weddings?

Yes - this issue is the bane of my existence (and of every rotational player I think). The amount of time and effort I have to spend to constantly re-introduce sims to their in-laws, distant cousins, former roommates, etc. after switching households is enormous.

I understand that the game needs to cull relationships to reduce lag, and it makes sense to me that sims might forget acquaintances that they only met once or twice, but for me the most frustrating thing is that the game doesn't account for situations where a person might not have a strong relationship with someone, but wouldn't simply forget them - like the instances I mentioned. It seems to me, for example, that if a relationship reaches the "good friends" level, the relationship with that sim should be safe from culling even if it fizzles out. You wouldn't forget someone you were once good friends with. And you certainly wouldn't forget your in-laws, even if you have a distant relationship with them.

As a more realistic workaround, I would simply like to have a toggle where I could mark certain sim relationships as safe from culling, like the game automatically does with parents and siblings. It would be a huge QOL upgrade for rotational players 🙏

Having this issue too. I'm a rotational player with many households. So I haven't played this one household in a few days, when I looked at the relationship panels almost every relationship bar is EMPTY, even with his own brother.  He's also befriended a lot of his co-workers + ppl outside work and those are apparently forgotten too, like completely gone from his contacts. 

Now before you say, get rid of mods repair game etc, I did. I don't think it affects this issue because the lost relationship + contacts can't be regained after it has already happened. Other households does not suffer this issue.

Some minimal troubleshooting I did are:

• Brother got married and moved out of this household into his partner's house.
• Is it possible that this Sim got affected by a memory wipe power of an alien? I've never played aliens before so I don't exactly know how their memory wipe power works.

It's not the end of the world as I can cheat all these relationships back but it'll be such a monumental work because this Sim has a lot of friends :|

Thank you