I suspect it may be related to the black hole system I had just discovered.
Further on this, the ship in question finally ran out of fuel 2 and a half years later, however, it has now been sitting in the middle of the black hole for 3 hours (game time, keeps stopping every 30 minutes to tell me it's out of fuel), without any apparent ill effects. Is death by black hole normally this prolonged? It's going to be really embarrassing if the ship named after the captain is launched before he actually dies.
editDecided to end their suffering and mine, set task force speed to one.
This generated an error popup.
(error 6 : overflow)
Attempting to set the speed to 1 again generated the same error popup.
Speed set to 1900 with no error.
Advanced time 1 day : SV King George V has been destroyed by a black hole!
So apparently not having any fuel doesn't prevent a ships engines from counteracting the pull of a black hole, even when technically it has spent the last 2 and a half years inside the black hole, due to the previous warping incident.
2nd editOh, almost forgot, the 3 unidentified wrecks in the black hole system haven't budged.