I realize cygwin isn't truly linux but wasn't sure where would be more appropriate. I have a script setup to download files from a remote server then delete them from the server it has ran fine for the better part of a day every couple minutes. unfortunately it stopped working and when i tries running it manually it seems to connect and see folders but when it gets to a file it immediately exits the program saying there was a problem with an assertion. Since some of my programs require windows going back to the linux comp that worked for months would mean running to comps at home 24/7 which is less than ideal. i've tried restarting the windows computer and the remote linux server and it still behaves the same. the terminal output is below i would greatly appreciate any help you can give.

assertion "stack_ptr>0" failed: file "/home/ASchulma/dev/cygwin/lftp/lftp-4.6.4-1.i686/src/lftp-4.6.4/src/SMTask.cc", line 156, function: static void SMTask::Leave(SMTask*)
./synctorrents.sh: line 27: 4808 Aborted (core dumped) lftp -p 21976 -u "$login","$pass" sftp://"$host" <<EOF
set sftp:auto-confirm yes
set mirror:use-pget-n 10
mirror -c --Remove-source-files --parallel=10 --log="$HOME/lftp/$base_name.log" "$remote_dir" "$local_dir"
quit
EOF

Perhaps something, let's say program B, overwrote a library used by lftp. Suggestions: Reinstall lftp (which might break program B), or use a different ftp client.