I had a similar case a couple of days ago. When I looked at the NPRs, a NPR-1 taskgroup was chasing a NPR-2 survey ship around the system. Because the TG and the survey ship had exactely the same maximum speed, this looked to be a neverending story. I changed the survey ships order to close with the enemy and everything went back to normal shortly.
To do something like this, you have to ask Steve for the PW for "designer mode" because only then you can see the NPRs
NOTE: Changing stuff in this mode is dangerous, because the AI can be easily brocken by changes you do! I strongly adivse to make a backup of your database beforehand!
Or, you can ask Steve if he can look at your database. Perhaps there _is_ something stange going on.