Posted by James Denneny on URL: http://elecraft.85.s1.nabble.com/K3-Firmware-Uploads-tp3917000p3920318.html
Do not use a usb/serial adaptor with K3 Utility. Dick N6KR suggested I
change to straight RS232 serial connection. That largely cured problem. I
still get an occasional failure of FPF or DSP1 with RS232 serial cable but a
repeat download always captures the file.