This is getting stranger and stranger. I have a fleet with active sensors sitting on top of a group of wrecks that have all been salvaged by a spoiler salvage ship and I still cannot pick it up on sensors - really odd. I think I'm going to have to delete the spoiler ships from the DB - any advice on what fields to modify other than FCT_Fleet and FCT_Ship?
I'd suggest not doing this because it is likely to cause some bugs, since fleets and ships intersect with several other mechanics/tables.
What might be more useful is to look through the spoiler fleets and identify what system they're in. There have been some weird bugs involving spoiler ships acting like they're in one system while being in another system in the past.
Attaching the DB here, alongside such analysis, could be more useful to Steve.