geosub1978 - I notice you are using the 1.4b Assisted Plotting Mod. This gave me similar 'Ship spotted' grief, a while back.

It might be worthwhile you checking your Contacts.cfg file. If the Decay Time For Precise Sensor Contacts has been set to 0, then change it back to the default GWX 2.1 setting of 60. Then test to see if this helps at all.
Good luck
Trefoil.