Issue is, do you get an additional 404 Not Found error when trying to access a non-existent file which should actually be redirected to an ErrorDocument.
For eg, when I try to access the following (noactualfile) :
The requested URL /~joelta/noactualfile was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
How to remove the above error log for the error document ?
Fix : Use the following lines in the .htaccess of the domains in question
ErrorDocument 400 default
ErrorDocument 401 default
ErrorDocument 403 default
ErrorDocument 404 default
ErrorDocument 410 default
ErrorDocument 500 default