Sims forget already existing relationships

I have had this happen multiple times in my current legacy (currently on 3rd gen., long lifespan.) I hadn't realized it at first as they knew a lot of other sims. What made me notice it was in my second gen. when the dad had completely forgotten their dog who had died; the father had the highest relationship with the dog, but everyone else in the household had remembered the dog when it came back as a ghost. After this I started to notice they were forgetting many sims- their daughters friends who visited often, some of their lower acquaintances, relatives (the grandmother), and even friends. 

Soon after their teenager moved out with her friends, and I have only noticed a couple forgotten sims. But admittedly haven't paid much attention to it as they are busy and don't socialize much. They have forgotten some peers they go to high school with.

At the time I did not have any mods installed, but I have two now. I have all packs except for Journey to Batuu and most of the kits.

There is no specific team to look for bugs in the game, we players needed to keep reporting things here. Everyone is worried about releasing more game packs to get more and more out of us players.

I have the same issue. On PC no mods or CC used.

My sims were in love and then suddenly they forgot they even met and I had to reintroduced them to each other. Then I rebuild the relationship and it happend again while they were on their honeymoon.
And I didn't switch families in the meantime.

Oh my god! Really? This is very difficult, I prefer to wait for you to one day find the mistake and correct it. I give up trying to pass on any error here in this forum. Thanks for the help.

EA is looking for saves so it would be great if you could send yours as instructed here: [INFORMATION] How to Send User Files to The Sims 4 Team | EA Forums - 5048472 

Please DM the link to EA_Cade

I don't use mods. I build relationships in the game, and when I switch families, and return to them, those Sims no longer have any relationships. 

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Could you give some more details what you are seeing as there are several issues.

Is this about romantic relationships decaying fast or you having to reintroduce yourself to Sims with rotational play ?

Also any mods and what platform ?

Personal relationships with acquaintances disappear.
When we meet again, we will exchange first-hand greetings.

I used the translation function.