[1000mp] Intermittent CW transmit lockout

[Rick Tavan N6XI]

Every once in a while, my MP (mark nothing) will refuse to transmit on CW. I
believe it happens only after a power-up, not suddenly during normal
operation. I confirm the problem is not in my SO2R switching by plugging an
unused phone plug into the KEY jack and shorting it. Nothing happens. The
other rig continues to work normally. Then I poke around at the usually
suspect buttons such as MOX, VOX, MONI and BK-IN, even though I am sure they
are set correctly. Sometimes when I do that, the rig will go key-down for a
while, then stop transmitting either all by itself or when I poke another
button. Sometimes it seems to go key-down indefinitely (until I power it
down). When the problem is active, VOX SSB works fine. After several power
cycles, the problem goes away. I got it to go away once by entering the Menu
Set sequence, changing nothing, and hitting ENT. I use Writelog and
sometimes it has been running but inactive prior to the problem. When that
is the case, I terminate WL but leave the MP connected to the computer via
its serial connection through a Serial to USB adapter. I can't stimulate the
problem intentionally and it has only happened half a few times in the past
two or three years. Any ideas?

Thanks & 73,

/Rick N6XI