Game wants to give me a legacy badge I didn't earn when downloading my save on a friend's PC

[Cadrin]

I was playing Phasmophobia on my own PC. Then I wanted to play on a friend's PC when visiting him.
He also plays the game and has a legacy badge. I do not.
I logged on my Steam Account, (on his machine and his Windows user profile), since I wanted to use my save file and not his. I made a backup of his save folder, just in case, and let the Steam Cloud do its magic to download my save file.
Now I am greeted by the game telling me my level has been reset to 0, I have been fast-tracked one prestige level, and that I am to customise my legacy badge. It has the same level as my friend's.
How do I stop the game from doing that? I never played before Progression 2.0. Those levels are not mine, I don't want those.

Now it looks like my save file is contaminated, too. It seems the changes have propagated to the Steam Cloud. I tried deleting the AppData/LocalLow/KineticGames/Phasmophobia folder and starting the game up again. However, it says it successfully downloaded the save data from the Cloud. Then it proceeds to the Progression 2.0 information screen and then to the legacy badge customisation.
What files govern the awarding of the legacy badge? What do I need to delete to make this stop?
Is there a save editor available? How do I edit my save file so that it stops saying I have legacy levels and am eligible for a badge when in fact I am not?