Shariff facebook sharing - main page instead of subpage content

I try to work with shariff on my kirby template. Sharing with twitter works fine; twitter is showing the correct content.
To share with facebook the default facebook/sharer.php get’s called with the url. But, facebook will use the content from the root url. Is this a effect of url rewriting?

The result will show the main / homepage content instead of the content from the given subpage link.

https://www.facebook.com/sharer.php

Without seeing your code it’s a bit harder to help, but here is what I use that works:

<a href="https://www.facebook.com/sharer/sharer.php?u=<?php echo rawurlencode($page->tinyurl()); ?>" title="Share via Facebook" target="_blank">
      <i class="icon icon--facebook"></i>
</a>