[Elecraft] K3 Transmit Pulsing When Cold

[W2LE]

This has been going on for years, about time to look into it.
K3, sn 1114, 100 watt, connected to P3.
K3 firmware 4.67, P3  1.26
Most mods have been done.

When the K3 is turned on cold (P3 configured not to come on with the K3) 
in CW mode transmit will start pulsing.  (Don't usually use SSB, so 
don't know what happens then.)
Sometimes it won't start doing this until I turn on the P3.
I usually put it in test mode and let it warm up, then it works fine all 
day.

It happens with all external connections (key, mic, MK2R+) disconnected.

I've reseated the internal P3 cables and reloaded firmware, no change.

Any ideas on other things to try?

Paul  W2LE