I think my save might be about to corrupt?

I was playing multiplayer last night with my girlfriend as the host, and I noticed that SMAPI was showing red text looking for one of my other saves (not the one I was currently playing on). I didn't think anything of it last night, but today when I went to play that save (Chet), it was gone. I looked at the save file and the old file and both were blank, so I wrote that entire save off as lost per the recovery post. Today, when I played multiplayer again, I noticed my SMAPI was still looking for Chet's game and throwing up error messages. Also, when my girlfriend tried to warp to the beach, it put her on her horse in the middle of the water instead of where the beach totem is supposed to go. Her SMAPI shows no error text, and we both have the same mods running in our games (mostly dialogue overhauls). I also noticed I now have three children in my house instead of two (each with their own names). I'm worried that the save might be corrupting, but this is our longest save ever and I really don't want to lose this farm. A few questions:

1) Why is it looking for Chet's save when I'm playing as a farmhand on a different save?
2) Is this a sign that my game is about to explode?
3) Why did Chet's save corrupt, and how can I prevent this in the future?

 

The game still checks for save files on your computer, which is when the error occurs. Save corruption usually happens when the save is interrupted (e.g. you exit the game while it's saving), but it's usually easy to recover the save. It's odd that the _old files were blank too, but you can also recover a backup from save-backups in the game folder.

The other issues you mention (e.g. being warped into the beach water) sound unrelated, but I haven't seen those issues before. What name does the mystery child have?

 

Apparently the beach water bug is related to touching the obelisk while on/touching a horse. The mystery child is named Baishe, and is in the baby/crawling stage like my second child (Cena). I also have one fully grown child (Millie). I can greet each of the children individually, and Cena has one heart while Baishe has zero hearts in my display.

 

I have no explanation for the mystery extra child. The game normally doesn't allow more than two, so I guess it's a bonus!