My Kenwood TS-450SAT is giving me the warning " UL " Which means PLL Unlocked. What would cause this? everything works fine, the receive screwed up though. if i tune to a local AM station i get no reception , move up a bit and back down again it is cutting in and out, move up some more and back again and its perfectly fine. After a 10 min warm up period the radio is back to normal will no warnings.Is there anything i can do? Is it a expensive repair?