I know other users have reported SEF errors and the Joomla core seems to fix them, but I think I've stumbled on something new (at least not reported here).

When using the Joomla SEF on a slave site, any article that has a direct menu link works great. Any menu item that links to a section or category works great too...until I click on an article. Then I get:

JFTP::mkdir: Bad response
JFTP::chmod: Bad response
JFTP::write: Bad response

Of course, that looks like an FTP layer problem, so I checked and re-checked all of the permissions for the master and two slaves (content is sharing from one slave to the other).

Finally, I turned off SEF and everything worked great.

Is there a way around this? Is it truly an FTP issue, or is there a problem with sharing data (I thought this was accomplished through the database, but I know there's a cache created somewhere of the articles)?

The two slave sites are subdomains, have the same FTP username, password, and permissions, but have different absolute paths.

It is very difficult to tell you which peace of code call the mkdir, chmod and write.
As you , I can just suppose there is a cache somewhere on the disk that require the creation of a directory and change it permission before writing in it.
Based on your description, we can just suppose this is somewher in the SEF extension that you are using.

If this is the native Joomla SEF, this is strange as we are using it without problem (but without the FTP layer). Perhaps this is an issue in joomla itself when using the FTP layer.

I will try without the FTP layer and report back. I did not go that far in my previous testing.

Should have done more testing, I guess.

Leaving the FTP layer enabled, but *manually* setting the 777 permissions to the appropriate directories in the master and ALL slave sites seems to have fixed it.

Apparently there is just some item that does not get accessed appropriately by FTP, but having full permissions fixes it.

Since there were no error logs, FTP logs, or access logs with the specific problem directory, it's difficult to know what exactly fixed the issue.

But I guess we know that at least with FTP layer enabled, directory permissions (as listed in the Joomla System Info page) must still all be manually set to writeable outside of FTP.

Thanks!!!