[Elecraft] RF Gain Calibration failure

[Tyler Barnett]

K3 SN 8341 kit, 100w final not yet installed.
Finishing up the calibration sequences.

Downloaded the Mac version of the K3 Utility and started it.
Connected Mac Mini to K3 using supplied KUSB.
A very good silver-plated 2 foot jumper is between the K3 ANT1 jack and a Heathkit Cantenna.
The KUSB cable is well clear of the coax and dummy load.

Started the 5W transmitter gain procedure.
And here is the failure, apparently on 20M:

Elecraft K3 Utility for OS X Revision 1.14.4.22
OS X Version 10.9.3 
K3 MCU revision 04.83. RS-232 speed 4800 bps.
Starting 5 watt calibration.
Calibrating at 1.900 MHz
Calibrating at 3.750 MHz
IsSamplingComplete: Unexpected response 'DS@@@@1�>I��;' to 'DS;'.
Calibration power settled at '  5.2 W ;'
5 watt calibration failed.
Elapsed time: 11.4 secs

What should I do next?

73, Tyler N4TY