WORKING:
...
debug1: Sending command: /usr/bin/ksh -c "cat /etc/passwd"
debug2: channel 0: request exec confirm 1
debug2: fd 4 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel_input_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_confirm: type 99 id 0
debug2: exec request accepted on channel 0
debug2: channel 0: rcvd eof
debug2: channel 0: output open -> drain
debug2: channel 0: obuf empty
debug2: channel 0: close_write
debug2: channel 0: output drain -> closed
...

NOT WORKING:
...
debug1: Sending command: /usr/bin/ksh -c "cat /etc/passwd"
debug1: channel request 0: exec
debug1: fd 4 setting TCP_NODELAY
debug2: callback done
debug1: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel 0: rcvd adjust 131072
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: channel 0: write failed
debug1: channel 0: close_write
debug1: channel 0: output open -> closed
debug1: channel 0: rcvd eof
debug1: channel 0: rcvd close
debug1: channel 0: close_read
debug1: channel 0: input open -> closed
debug3: channel 0: will not send data after close
debug1: channel 0: almost dead
debug1: channel 0: gc: notify user
debug1: channel 0: gc: user detached
debug1: channel 0: send close
debug1: channel 0: is dead
debug1: channel 0: garbage collecting
debug1: channel_free: channel 0: client-session, nchannels 1
debug3: channel_free: status: The following connections are open:
  #0 client-session (t4 r0 i3/0 o3/0 fd -1/-1)
debug3: channel_close_fds: channel 0: r -1 w -1 e 7
debug1: fd 1 clearing O_NONBLOCK
debug1: fd 2 clearing O_NONBLOCK
Connection to host closed.
debug1: Transferred: stdin 0, stdout 0, stderr 30 bytes in 15.1 seconds
debug1: Bytes per second: stdin 0.0, stdout 0.0, stderr 2.0
debug1: Exit status 0
...