[Elecraft] K2 hangs when using TUNE

[Simon & Liz Watts]

K2 builders,

I have a K2/100 #3834 with KSB2, K160RX and using a KAT100.
Occasionally, I experience a malfunction when using the TUNE function.  The transmitter starts to transmit and then the whole set freezes with low current drain, the receiver is dead and all buttons are inoperative.  The K2 has to be reset by switching off and then switching on again.  This state may persist for successive applications of TUNE for some time but on each occasion so far it has eventually reverted to normal working.  When present, the fault persists after the KAT100 is disconnected.

Does anyone have any suggestions as to what may be causing this? 

Simon