I haven’t encountered that issue. Can you simply reinstall it, or something, or is there a limit on your ability to do that?
If the connection falters, Filezilla will try to “retry” and resume upload/download… if it reaches the max retries, it’ll fail and stop trying to resume. One way to combat this on a poor connection is to change the max number of retries. Go to Edit->Settings and under Overview, “Maximum number of retries” seems to default to “2”. “0” is unlimited, I believe, and obviously a number higher than 2 might help as well.
Do you have any specific information about the errors, can you show us a log file, or tell us file sizes you’re working with, Internet connection reliability, etc? It’s hard to troubleshoot a problem with so little information!