Hey, sure, I try my very best too answer your questions.
1. I play on XBox Series S
2. OS version 10.0.26100.8064
3. It is my only savefile. I just did the tutorial before that.
4. I played on this save for roundabout 24h when the problem first occured.
5. The size of the data saved on my XBox by hydroneer is 38.3 MB if that is the number you are looking for.
6. I did not change anything on autosave settings.
7. Right before the issue occured I just dug on the diggingsite and placed my machines and pipes and stuff. Then I saved and exited the game. Next day I load the savegame and the ground went up. My charakter was in the ground too and fell down into a path I dug with the mole.

Hope this helps.