There's a very knowledgeable group of people at this Yahoo group:http://groups.yahoo.com/group/TS-850_450_690
Feel free to join!
The TS-440 is notorious for its VCO unlock problem due to a contact cement Kenwood put on the VCO part of the circuit. I successfully repaired mine by taking every component off that board and cleaning off all the glue. Very tedious, but worked fine afterwards.
The TS-850 has a similar problem but it hasn't happened to mine yet. I think it's due to some other cause, as there's no contact cement on the VCO circuits in the 850 AFAIK.