I have no clue what's triggering this, but whenever I load a save, or even when I start a new adventure, my PC's colon is stuffed with cum, even getting the status effect "Stuffed: 2"

I checked the save files and the starting condition is set to {} as it should be, but the current condition is set to Stuffed even as early as spawning on the map. Hell, he's even listed as a virgin but stuffed full of cum.

I tried deleting all the save files, but the problem persists.

You're using a bugged version of the game - if you're a patron, just download the most recent build in the build folder for the hotfix.