Spawned in a big ship with plenty of turrets and docks, when the mothership was despawned. Some of the turrets/docks were non physical, others were fine.
Seems that usually 50% of them are non physical, and the other half is fine.
Despawning the ship that contains those docks causes it (can be overheating or /destroy_entity).
Blueprint that always has 1 of the 3 PD turrets non physical, which one seems to be random though: {F7441}