No I mean the actual vender of the FTP server software, such as proftpd, vs-ftpd, pure-ftpd, etc, typically this is shown in the first couple lines of the server session window.
Please try the following test build and let me know if it resolves the problem for you.
https://oss.azurewebsites.net/testr/FlashFXP41_1702_Setup.exe
I am unable to find a server to reproduce this issue, I am working in the dark and not really knowing if the changes I make will actually fix it or not.