during recent testing of foobar2000 mobile version for iOS I had issues with uploading tracks via its built-in FTP server via Total Commander.
Filezilla went fine, so I tried to find the culprit.
Basically, all uploads from TC gets retried up to maximum attempt count, because there is upload size mismatch.. in another words, after upload finishes, TC fetches the size of uploaded file from server and compare that with local file size, if values doesn't match, it reports error and tries whole upload again.
It apparently won't work with all servers though (likely incompatible file size listing.. it would need better analysis of issued FTP client commands and server responses).

But there is configuration option in wcx_ftp.ini, which overrides that behavior and defeats mentioned upload size comparison.
Section [General] , add the line:

more info from TC author..

This does the trick also in the case of foobar2000 FTP server

All the best,