[Elecraft] K2 CW dot problem

[Dave G3VGR]

My K2 has developed a strange problem when using the keyer on CW. If I 
press and hold  the paddle for dashes, it sends a string of dashes 
correctly. If I press and hold the paddle for dots, it will send only 
one dot, then on releasing the paddle, I hear 2 lower frequency dits and 
the rig switches from the current VFO to the other VFO.

I removed the control board & checked the tracks from P3  pins 17&18 to 
the MCU, no shorts, opens or solder bridges.
Looking at the schematic,  it all looks very simple, just grounding pins 
29 & 30 of the MCU to send code.  Can anyone suggest what I should try next?
-- 
73, Dave G3VGR
K2 #4783