xmodem and ymodem repeat initial block
Both xmodem and ymodem repeat the initial packet of a transfer even though the initial packet is acknowledged. In the case of xmodem, packet sequence 1 is sent, acknowledged by the receiver, and then sent again by tera term. In the case of ymodem it will be packet sequence 0 with all the file info that is sent, acknowledged by the receiver, and then sent again as if the receiver had NAK'd it.
Root cause found - see #37456
and workaround proposed.