Help, Desync since Version .15.9

[Dingus69]

Hello , me and a friend where playing this map for about 12 h and since we updated to 15.9 we are getting desyncs .
We cant downgrade through steam , it just stays at 15.9 D:
Is there a way to downgrade the game back to 15.7)
Sometimes the game crashes, but only for me , we allready made sure we have the exact same mod versions.
I hope you guys can Help us. I uploaded the Files on Mediafire, its too large for an attachment.

https://www.mediafire.com/?61csp7bdwmh70nj

My Thanks ! - Felix

(sorry for bad English)

[EldaRion]

With us the same

1 Player can join.
With the 2 Player Desync-loop.

[FuzzCat927]

There's a way to downgrade through steam. Instead of opting into 0.15.x via steam, just opt into a previous version?