[Elecraft] KPA500 Shifting Bands without any change in K3 Frequency

[Joe Rogers]

I am operating the KPA500 KAT500 power combo with the K3.  The combination works great and normally makes frequency and antenna changes really simple.  I operate on MARS frequencies and normally all works just fine outside of all the amateur bands with the KPA500/KAT500/K3 there is, however, one frequency where there is an issue.
When transmitting at about 4.5 MHz using SSB or digital modes, using the KPA500/KAT500/K3 combination, the band indication shoes the KPA500 spuriously shifting back and forth between 3.5 and 5.3 MHz bands.  This also affects the amplifier output power. I can also hear what sounds like contact/relay cycling.   This makes the combo unusable on this frequency.
How can I resolve this problem so that the KPA500 is usable on this frequency?
73
Joe AJ1Y