Thanks so much for your help and info. The current computer that I'm using is a fairly new Sager gaming laptop that I purchased with the "less bloat" option of Wndows 10 (you can choose to either have the whole mess of the OS or streamlined with fewer bloatware apps). Which leads me to ask if you think it could be that I'm missing some system bloatware app? Hmmm.
Or, have you heard about any issues with Sims 3 on a machine with an SSD and an HDD? In my case, the system and Sims game files are on the SSD C drive and the Electronic Arts folder is in the user Documents folder on the D drive.
Aside from these weird closing out task issues, the game runs fine without noticeable lag or glitches while in the game. I know laptops are generally frowned upon for playing Sims, but I played it with all expansions installed (!) for years on my old HP Pavilion laptop without issue as long as I had an external fan going.
Thanks again for your vast knowledge!