Vassals almost immediately declaring war on me after subjugation [1.0.7.3]

[giltirn]

Twice I've beat down my Ackdarian neighbors and subjugated them, but both times within a short period we are at war again, and they are claiming that I broke the defense treaty. I am absolutely certain that I did not order an attack after the war ended.

I did not ask for a defense treaty, and can only assume that it comes as part of the vassal deal. Certainly the second time I beat them down I ended the war using the "demand vassalization as condition to end war" option in the dialogue box, and so I could not have accidentally also negotiated a defense treaty.

I've loaded a save game from just before the treaty is broken that can be found here: https://easyupload.io/vnv14x . The issue seems to be 100% reproducible; shortly after loading the game you'll see the vassal treaty break and the Ackdarians become very upset. It's easy to confirm there are no military ships with orders to attack from my side at least, and I couldn't see any aggressive activity from their fleets.