Don't know if this is a bug or just undocumented, but it seems as you should turn off autovacuum before you run CLUSTER, otherwise you might run into a deadlock:
NOTICE: Clustering idx_vehicle_unit_data_200407_person_information__id on vehicle_unit_data_200407
ERROR: deadlock detected
DETAIL: Process 29022 waits for AccessExclusiveLock on relation 68950 of database 16390; blocked by process 15865.
Process 15865 waits for AccessShareLock on relation 68122 of database 16390; blocked by process 29022.
/Mikael