FileZilla: connection unreliable

Does someone has experience with current versions of filezilla when transferring large number of files?

I had to shift some server contents to other location. Ok , took the tool I was using frequently so far, the filezilla portable. But to my surprise the connection was very bad, many repetitions of files transmission, all taking time for ever etc.

Tried then the very old wsftp, and all was perfect, also tried the fireftp in the firefox and this went also fine.

Are any known issues or can the filezilla be somehow tweaked to work as it used to?