This is new to us:

150 Opening BINARY mode data connection for XYZFILE2.
REMOTE ABORTED THE CONNECTION. (SOCKERR 64)
426 Connection closed; transfer aborted.
SUCCESSFUL COMPLETION. (SOCKERR 0)

Has anyone else had the pleasure? We have been happily running this job in
some form for a year and a half, and I have seen some interesting problems,
including a few too many SOCKERRs, but this is a first, where an error was
not seen as an error(?!).

Our command file has EXITONERROR, and this is inside a loop:

!SETVAR FTPLASTERR 999999999
!WHILE FTPLASTERR <> OK AND NOT FTPCOUNTER > 9
! RUN FTP.ARPA.SYS;INFO="NTftpserver";STDIN=XYZFILE2.CONFIG

This has done the trick before, when we had SOCKERRs, looping until it
works; nine tries is either more than enough, or there is a much bigger
problem so that no number of retries makes sense. And normally, this works
on the first try. But having ftp end with FTPLASTERR OK because there was a
SOCKERR 0 * after * a SOCKERR 64 is a bad thing.