One thing not mentioned here is that I have found this error (Error: Failed to convert command to 8 bit charset) can also be generated from Filezilla when files and folders have first been transferred from a Mac to a PC before being FTP'd and contain non-standard Mac characters. This is a known issue and there have been custom apps that have been built that will automatically correct the non-standard characters.
-So what's the resolution to this? where are these custom apps?
List of Charsets names used in Filezilla
These should be documented or pointed to here.
Bug when transfering utf-8 include files for PHP with Filezilla in ASCII mode
I had exact this error now in Filezilla 3.44.2 Filezilla Version history does not mention this severe bug: https://filezilla-project.org/versions.php
This is not a PHP issue!