Perfectly tagged MP3s but MP3 Diags says it's got a lot of garbage

see here:

(it is currently not possible)

Please note that this is a warning and no real problem ... unless your player cannot cope with progressive jpgs.
The progressive format is a valid jpg format. It is just that some application developers took a shortcut and left out the handling for this picture type.
So if you see all the pictures in you players, leave it as it is.

Oh, and the filter has to follow a syntax as described in the documentation:

You are missing a filter keyword.