product_canonical doesn't deliver correct canonical url

product_canonical doesn't deliver correct canonical url -SOLVED

in order to present one product in different categories and in one main-category as well without having double-conten i installed product_canonical - but it doesn't work as it should.
without that program, sef stated every categry as "canonical" with a link like
<link href="http://website/index.php/shop/main-category/sub-category/article" rel="canonical" />
after installation of product_canonical an sef set inactiv, the main category is displayes without an "canonical" - OK.
But the subcategorys are displayed with this kind of link

<link rel="canonical" href="/index.php/shop/main-category/sub-category/main-category/article"/>
so
how to truncate the displaced string "sub-category/main-category"

Is there any bux-fix?

thx

Jürgen

SOLVED
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what i had to do?
in SEF i deactivated line 50 so there are no double "canonical"-links. The 2nd problem was a mismatch in the database - not a problem within product_canonical

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