@NiLuJe
Got it, thanks!
Also I noticed that (most probably) these logs I described here appear when I successfully sftp to Kindle with usbnetlite (5.16.21):
https://www.mobileread.com/forums/sh...d.php?t=363853
How should I diagnose it?
I can temporarily enable showlog & co. Anything else? (Strace, debug logging of usbnet, or maybe WinSCP side on PC?)