Sims forget already existing relationships

I am having the same issue - even with smaller save files. Sims keep having to reintroduce themselves to other sims they have met before. No mods but CC. This is happening in all of my save files. 

Ever since the update I have had Sims that I know my Sim knows randomly just vanishing from their list of people they know. Sometimes they are just acquaintances, sometimes they are even friends. They just vanish with no reason or explanation. If I go to the household of the Sim that vanished, they know longer know that Sim either.

It's really wrecking immersive gameplay and storytelling. 

my sims cannot make friends with other sims cause the whole progress gets deleted. its only about sims from outside the family. inside the family relationship progress saves just fine

My Sims keep forgetting relationships. They forget even when friends. It seems to be worse with the household that is being played most. It's getting annoying having to introduce self again multiple times every play session.

I'm having this issue now. Sims forget relationships even when friends or higher.