redirection to /marktest results in /marktesttesttesttesttesttesttesttesttesttes

Hi im using the redirection plugin by automatic on a windows server running php (so no .htaccess). ive setup a test redirection from /mark to /marktest but when you enter the former into the URL bar you end up at /marktesttesttesttesttesttesttesttesttesttesttesttesttesttesttesttesttesttesttesttesttest which is obviously an issue. Any idea how to fix this?