Unwanted Autonomous Alien Memory Erase Issue

I don't know what triggers it, but I've had it autonomously happen to mine a couple of different times in the past. Once was while my sim was in the romantic stage of her relationship. At the time I was thinking well maybe he doesn't want to be involved with my sim, but he kept coming around and eventually they were married and had a couple of children. Throughout their whole marriage, everything went fine until just before he passed away. He ended up pulling the same stunt on his wife again. That was the only time I ever had any issues with that.