Minecraft Version

1.12.2

Forge Version

14.23.5.2838

Mod Version

Within FTB Ultimate Reloaded 1.8.0

Describe your problem, including steps to reproduce it

Me and my friend were playing local coop. He placed a water bukkit in the item router and then
my game crashed.

I hosted the server, so my friend just got a shutdown message. I was back in the minecraft launcher with the attached error message.

If I try to launch the map again it instantly crashes with same error message.

Any other comments?

We are new to the mod and he tried to manage fluid transportation.

Edit: There also was a puller-module and a fluid module in the item router. After inserting the water bukkit manualy it crashed.