They obviously forgot to program some AI logic like this:
For all ships whithout task:
- Is it a planet buffing ship?
- No: go on with normal ship logic
- Yes: Is ship already in orbit of a planet that profits from buff?
- - Yes: do nothing (or look for a better planet within a certain range)
- - No: find planet that profits the most from buffing within a certain range (to prevent the ship from travelling 50 turns and squandering the buff meanwhile)
Or perhaps they have the logic but it doesn't work. Above pseudo code fails if ships are automatically given a default task (like scouting) on creation.
If they forgot the logic I presume the probability for a fix is low. If it's just an error a fix is more probable.