start a new game. data corrupted by updates

Damn, it really do be like that I guess.

Well, at least that save was a fun run while it lasted.

happens every couple updates. gl n hf in your new run

So the save that I sunk the most time in is lost because this mod auto updated itself? Yay.... Not starting over.

Don't be lazy and download Perisno from moddb manually instead of steam.
In descriptions of moddb versions it's always clarified what they are and aren't compatible with.

I don't think it's laziness, I think it's a broken system. I have multiple other mods downloaded from Moddb, for example multiple versions of POP. How could I know this would be a problem?

Originally posted by Lt. Sharpe:

I have multiple other mods downloaded from Moddb, for example multiple versions of POP.

Man, you're proving my point.:)
Moddb good, steam bad.
Warband engine is rather inflexible when it comes to updates, it's not, say, Skyrim or FO4 which are made to be as mod- and update-friendly as possible.
So whenever you're considering updating an M&B mod while still playing it you have to carefully read the changelog and think twice. We try our best to make updates compatible but sometimes it's just not possible (but at the same time the update has to be released because it fixes critical bugs).

Originally posted by Lt. Sharpe:

How could I know this would be a problem?

You're too optimistic.
You should rather ask "how can I know there won't be any problems?". It's programming, it's complicated, and the realistic truth is that updates "fix some bugs, add others". And existing progress is especially vulnerable to such updates.
You should never auto-update anything hoping it will be fine, you should always assume the opposite, and only update things when you're more or less certain (after reading the changelog and any other notes left by the devs regarding the update). Auto-updates is the first thing you should find & disable after installing ANY software.