[ARCHIVED] Sims forget already existing relationships

Product: The Sims 4
Platform:PC
Which language are you playing the game in? Deutsch
How often does the bug occur? Every time (100%)
What is your current game version number? n/a
What expansions, game packs, and stuff packs do you have installed? Everything but My First Pet Stuff
Steps: How can we find the bug ourselves? Have a couple of households and play rotationally
What happens when the bug occurs? I noticed this issue in a save file where I play rotational. Sims forget relationships with sims they have met before and have even been friends with. I had sims e.g. forget their inlaws a couple of times and I have given up on re-introducing them after the fourth of fifth time. Same thing happens with colleagues in active careers. My sims have to re-introduce themselves to their work collegues every round I play with them, even to those they have been friends with when I last played them. I noticed that the relationships remain intact when they have been romantically involved with a sim (those they never forget, even if there's no romance and friendship anymore) and if I remember correctly those relationships where they have been "good friends" with another sim (not just "friends") also remain intact.
What do you expect to see? Sims remembering their friends/acquaintances
Have you installed any customization with the game, e.g. Custom Content or Mods? Never used.
Did this issue appear after a specific patch or change you made to your system? Neutral/Not Sure 

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Edit: family relationships aren't affected either

Edit By Crinrict: Adjusted Tag