Hello.
They are very bugged and stupid in many ways. There is just a pointless war that takes really long time. It's not just HRE, it involves the whole of Europe, and the League choices are stupid - for example Catholic France was fighting for the Protestant league in one of my games. I'm writing this post after I needed to fight against my vassal in a League war, they got sieged by me (I wanted them out of the war) and the war leader decided to give most of their provinces to one of my rivals...
They are very bugged and stupid in many ways. There is just a pointless war that takes really long time. It's not just HRE, it involves the whole of Europe, and the League choices are stupid - for example Catholic France was fighting for the Protestant league in one of my games. I'm writing this post after I needed to fight against my vassal in a League war, they got sieged by me (I wanted them out of the war) and the war leader decided to give most of their provinces to one of my rivals...