I think that the 'stuck' mechanism is the method by which the game handles re-fueling operations. Of course, the designers could always have forced the tankers to circle at loiter speed to allow the aircraft coming to refuel to catch the tankers, but the freeze/stuck is a close approximation of the rendezvous process.
The only thing I can think of to recommend, at this time, is just to try and re-plot new courses for the aircraft and possibly changing their speed/altitude.
If you have a saved game with the 'stuck tankers', please feel free to attach them. Often, a saved game file is the fastest and easiest way to run down problems. If SubSim is unable to accept a file as an attachment, you can always post them to the HarPlonkedHQ site forum.
http://www.harplonkhq.com/forum/viewforum.php?f=8