Back links to pages on our site that don't exist on forums we haven't used with irrelevant product anchor text

[rufo]

Hi,

I have a recurring issue that I can't find a reason for.

I have a website that has over 7k backlinks that I monitor quite closely.  Each month there are additional links on third party forums that have no relevance to the site or subject matter that are as a result toxic.

Our clients site is a training site yet these links are appearing on third party sites like http://das-forum-der-musik.de/mineforum/ and have anchor text with "UGG boots for sale" to pages on our url listed as /mensuggboots.html that obviously don't exist.

Each month, I try to contact the site owners and then I add them to Google using the disavow tool.  Two months later they are gone and then are replaced with new backlinks on a number of different forum websites.  Quite random but always relating to UGG boots.

There are at least 100 extra links each month.  Can anyone suggest why this is happening?  Has anyone seen this kind of activity before?  Is it possibly black hat SEO being performed by a competitor?  I just don't understand why our URL is listed.  To be fair, there are other websites linked to using the same terms that aren't ours and are also of a different theme so I don't understand what the "spammer" is trying to achieve.

Any help would be appreciated.
KInd Regards
Steve