Unfortunately, this did not fix my particular KX2. TX Gain calibration was completed successfully, but the same issue persists.
I also did the TX bias calibration, and noted that bis on Q6 took ~45 seconds to complete, vs the 3-10 the manual suggested. Q7 was fast. Q6 wavered a lot between .3-.7v. I suspect this suggests the problem is perhaps indeed hardware-related.
Thank you to everyone on the list who responded with ideas to check. I’ll get this one packed up and sent back to Elecraft.