Random crashing

[K. V. K.]

I am able to recreate the same scenario over and over again, since the crash happens at the start of February and I have an autosave. In this game, I am about to complete the imperial reconquest of a Welsh duchy, which I am only 2 sieges away from winning. On the second day, the (republican) duke of a random place in the empire accepts to sell me a favour, which I immediately use to make him end his plot war to revoke a county. Some days pass and the duke accepts a white peace due to the favour, I assault the last two holdings with minimal losses and offer peace to the king of Wales. After some days he accepts, the war ends and I get control of his former vassals in the duchy. This always happens. However, after this, the crash happens randomly after one of these actions... 1: I demand the conversion of a Nestorian count. 2: I use a decision to restore the province of Pontus (which was in Ck2plus, but I adapted it to the new map), making several duchies a part of the new province (a kingdom-level title), which becomes de jure part of the empire as part of the decision's effects. 3: I revoke the duchy I just conquered to give it out again as a viceroyalty. It should be noted that none of these actions cause the crash by themselves: it only happens after unpausing, either immediately or after a couple of days. What could possibly be the cause of the crash?