I have had some armies at sea that were tagged with attrition per turn, due to trespassing, but I was not able to move them until I gained enough war support to declare war to the faction, I have just asked for surrender.

the ability to move the unit was visible on the map as usual but there was no indication why they could not move.

savegame:
cannot move.ctr

expected behaviour:

all units should be able to be moved out of enemy territory when a war has ended.

example 

Screenshot 2023-06-07 000260.png