[Elecraft] A question about HDSDR controlling SDR & K3 at same time

[bw_dw at fastmail.fm]

So last week with your help I got HDSDR setup to control both a RFSPACE-IQ (for panadapter) and the K3 at the same time.

There is one behavior I haven't been able to figure out.

I have HDSDR and the K3 both setup to output a CW sidetone at 600hz.

In CW mode - HDSDR displays a close-up of a given signal on the lower-right.
And at dead-center its spot on - and producing the 600z tone.
But its then not quite spot on - on the K3

I've tried offsetting the side-tone frequency on HDSDR - thinking I just needed to shift it so that when the K3 is spot on - the signal will show up in dead center on the HDSDR signal window.

But that doesn't seem to work.  It still retains the exact same frequency offset between HDSDR and the K3

Has anyone seen this?
And can suggest a fix?

Thanks
Duane