Stage reset from stage 5 to below zero

[Fernlichtblinker]

Bug Description

I grinded through this modpack on one play-through since October 2021 and experienced nearly zero bugs so far, even with the past updates. Yet, after having a blue screen while in-game (world was fully loaded) today, I restarted the game, opened the save and all items got unequipped. I did not notice it in my base because all textures were normal, I was able to interact with all machines (stages 2 to 5), except this one torch with a changed texture to the primal age. I checked the advancement tab a had all the achievements I reached so far. Yet in the inventory when hovering over the items the overlay said "You don't know how ..." "You need stage ... first.
My test world was not affected at all from this problem.

I tried:
commands:
/advancement grant everything -> this gave me every achievement, but did not progress the stage at which the game thought I should be. I tried also the version with until ... for most of the end and beginning advancements of stages, which did not help.
/gamestage add stage... -> This also did not help. I tired every age
backups:
I used the backup function in the save overview. All backups from the same day were corrupted in the same way.

How I solved it:
This is quite weird. I closed the back-up where I tried out the commands from above. I reopen a different back up version from a day before and suddenly the problem was gone all stages were loaded correctly, even the back-up version / worlds in which I did not use any commands, had the correct game stage.

Did this behavior use to work in the previous version?

Not relevant

Steps to Reproduce (for bugs)

1.I don't even know how and why my "solution" worked.
2.
3.

Logs

• Client/Server Log: I don't know how to get it.
• Crash Log: Not avaiable

Client Information

• Modpack Version: 3.2.3
• Java Version: 8.0.2810.9
• Launcher Used: Curseforge
• Memory Allocated: 17120MB
• Server/LAN/Single Player: Single-player
• Optifine Installed: NO
• Shaders Enabled: NO

World Information

• Modpack Version world created in: The current version of October 2021
• Additional Content Installed: No