IP blocked by Server

Hi,

we have a big problem working on our site.

When i access the media section in wordpress and upload one (or more) files my IP is beeing blocked by the server (apache, fail2ban).

The server log states it is because my ip is trying to acces a file which is not allowed by dlm. In this case the user file is a pdf. But i am beeing blocked because of trying to access the coresponding JPG File (filename-212×300.jpg). I think because i am using the media section of wordpress.

So the .htaccess file in the dlm_uploads directory is set to “deny from all”.
In the forum is another post regarding this problem (dlm ip lock). This user solved his issue with allowing his ip in the .htaccess file. But we have dynamic IPs so this solution would only be a workaround?

Any ideas how to solve this problem?!

Thank you.