Single-player game with 7 AI opponents. One AI player (brown) temporarily closed borders using leverage, and I (green) received a grievance for trespassing. The only one of my units in their territories is a spy unit that was still concealed. Incidentally, one of their units was trespassing within a territory belonging to my vassal (light green).
Step by step of the bug
Step 1
At start of turn, opponent moves army into foreign territory that is normally open borders.
Step 2
Player orders units to complete actions.
Step 3
Opponent activates Expel Military Forces leverage action.
Single-player game with 7 AI opponents. One AI player (brown) temporarily closed borders using leverage, and I (green) received a grievance for trespassing. The only one of my units in their territories is a spy unit that was still concealed. Incidentally, one of their units was trespassing within a territory belonging to my vassal (light green).