Vehicle pathfinding frozen

Some of my vehicles are just sitting around. They'll take commands from a unit controller structure or the aai remote, but they don't move anywhere. If I select a vehicle, i can see a green line and target, but the vehicle doesn't move at all. If i try to send a vehicle to another location, the target doesn't move. But if i deselect and then reselect the vehicle, then the green target moves to where i clicked. The vehicles will still fire at any biters that wander close by, but the pathfinding seems to be broken. It only appears to be happening to some of the vehicles though.

Here's my savefile if it helps
https://www.dropbox.com/scl/fi/jtdb3wtpx2aapvfmxyfqc/se_sandbox.zip?rlkey=wgt2hnf5hzic0sligg8nxk3ey&dl=0