[Elecraft] KPA3 misbehaving

[Steve Reed]

Today my trusty K3 developed a strange and sudden problem -- I can't turn
the power output past 12 watts -- the KPA3 isn't clicking in!  It was
working perfectly yesterday, but today not so well.  Went through all the
menus, even tried resetting the radio from scratch and re-enabling the KPA3
in the config menu.  The fan test works fine, and the PA test works fine
too (I can hear the relay click).  But going past 12 watts with the power
control no longer works.

Anyone seen this before and know what the cause may be?

Steve, AI7AZ