You probably declared a few wars when they had high war exhaustion.
That's about the best way to have them dishonour.
(similar situation as Byzantium allied with Russia: they trust me "utterly", relations of 200, RM and all.. Don't even think of gobbling up a OPM when your ally has 10+ WE)
Once you're not allied., you're basically a big threat on their border as far as they're concerned. Add in a good CB (there's few better than Holy War, as in your case) and you've got a war waiting to happen.
That's about the best way to have them dishonour.
(similar situation as Byzantium allied with Russia: they trust me "utterly", relations of 200, RM and all.. Don't even think of gobbling up a OPM when your ally has 10+ WE)
Once you're not allied., you're basically a big threat on their border as far as they're concerned. Add in a good CB (there's few better than Holy War, as in your case) and you've got a war waiting to happen.