[Elecraft] K3 power output instability

[Arliss]

I'm experiencing a problem with instability in power output from 
my K3/100.  No word back from Elecraft yet (it's only been a few 
days), so I thought I'd try here.

The problem is that at relatively low power output levels 
(approximately 10 to 40 watts), the power output does not remain 
constant.   If I engage TUNE, the power will vary plus/minus 3 or 
4 watts, then jump up briefly by as much as 10 watts or more 
before resuming smaller excursions.  Although the power 
variations are brief, they cause the grid protection circuit in 
the amp to trip.  This behavior seems to be independent of mode 
and frequency.

The above problem persists with different feedlines and occurs 
with the amp out of line and transmitting into a dummy load as 
well.  At higher levels of output, the power level is stable. The 
radio is of relatively recent manufacture (S/N 5839) and I have 
the latest downloads installed.  I have another K3 that does not 
exhibit this problem.

Any ideas?

Thanks & 73,

Arliss   W7XU