Here is another type of error associated with contracts:
In one town, named Harlingen were available 2 contracts – Patrol and Delivery, both were negotiated and Patrol contract accepted.
One day later after battles and visiting two other towns Brothers returned to Harlingen completing Patrol contract, there previously
negotiated Delivery contract was still available. Opening negotiations and trying to Accept it did nothing, but return to town screen..
Save and Reload fixed it.
Reproducible 100%: load ‘2 contracts.sav’, negotiate both, and complete patrol.
saves and log attached.