Save game ID starts from the beginning all over again?

[dferstat]

So, I was happily playing Fallout 4 last night when my dog whined at me to tell me to go to bed. (Yes, with my dog this is a thing). So, I made a manual save, and quit the game.

This morning, I resumed playing. After several hours of play, I happened to look at my Save Games tab, whereupon I discovered that instead of numbering my first save of the day as ID 608, Vortex had given it ID 1, with subsequent saves up to ID 16. (Yes, I did have 607 manual saves; I have a PC made of cheese, running more than a few mods. Crashes are something I have to expect).

 

Does anybody have any idea what causes this, so that I prevent its recurrence? While I can manually edit the ID for a save, I don't want to have to keep doing this.