I think there's just not enough data for the snippet to compare with.. too specific?
It's looking for these terms only:
- gemeente woerkum
- onze
- diensten
In the resource parents 16 and 30.
The only resource fields it tries to find those terms in is the longtitle, and your "tags" TV. Doesn't sound like a lot of opportunity to find anything related..
You can try extending the field search (that may add more words to the match data as well) to include the pagetitle, or even the introtext or a summary TV.
If you are 110% sure there is matching data (so resources with one of those three terms, with as parent resource 16 or 30) I'd like to see it for myself, and tinker with the snippet a bit to see if it's a bug somewhere.
Could you email me at hello a-t markhamstra.com in that case? If you can share a manager login that would be great, else we could set up a quick Teamviewer session in which I look at the manager through your screen.