I have managed to reproduce this bug under more or less controlled conditions, although accidentally. I had a fleet of 3 ship ordered to Earth. 5-10 days later, not totally sure of their location I ordered them ?move to Earth?, ?begin minor overhaul? ?refuel from colony? the next event for the fleet said orders not possible due to ships in fleet undergoing maintenance (or a close approximation).
Once a ship is in overhaul, it won't obey any more orders until the overhaul is completed (to prevent ships under overhaul sailiing off into space). The warning you received would be for the refuel orders. If you are planning an overhaul, its best to make that the last order and refuel beforehand.
The fleet was stranded just outside the orbit of Earth, no movement vector but a speed noted next to it. I left it for 3-4 5-day turns, then through the task force screen transferred the ships to a task group known to be in Earth orbit. The ships duly completed their overhaul I transferred them back to their original fleet still just outside Earth orbit and off they went. When I checked the event log and the fleet in question had already arrived at Earth before I issued a second ?move to Earth? while they were in Earth orbit and it is this that appeared to upset the process but I don?t understand how they moved from Earth orbit to space! If I order ?move to Earth? then after their arrival ?begin minor overhaul? there is no problem even with conditional orders set.
Just to clarify, if you normally order "Move to Earth" and "Begin Overhaul", there is no problem. If you order "Move to Earth", "Begin Overhaul" and "Refuel" while the fleet is already in Earth orbit, this causes the problem?
Steve