If a patrol leader/captain was killed, the remaining follower will circle around a random area of where it's leader/captain died. Their PatrolTarget XYZ will be stuck permanently on one position near the patrol leader/captain's death. For example, the patrol in the attachment video death position is XYZ: 88.599 / 4.00000 / -112.599 and as I press F3 + N to get their data, their PatrolTarget is set to 82, 4, -110. Also affects snapshot 19w34a.

How to Reproduce

1. Spawn patrol captain and patrol followers (Commands are shown below)
2. When killing the patrol leader:

   /kill @e[type=pillager,nbt={PatrolLeader:1b}] 

1. The patrol followers would walk around the area where the captain died.

Workaround

Simply use the /data command to set their Patrolling tag to 0b.