Diplomacy is entirely broken

[Equilibrium]

I'd say it's not broken but simply their new principle of having arch enemies that they talked about in one of the daily updates.
Just like you I've not been able to make peace with poland at any time as prussia but with the russians, france and even the austrians after taking away two provinces and destroying bavaria for a small fee of money they all agreed to peace and have kept it so far.

[Lemur]

Hmm, okay, I'll re-start my UP campaign on M/M and see if that makes a diff.