Yep I did test that before I wrote.
I have an individual map for each, and that works – but the mashup will not show them.
An example can be seen here:
http://www.putandtake.info/vestjylland/baekmarksbro-put-take/
big map = the individual map
sidebar = mashup from the category ( http://www.putandtake.info/vestjylland/ )
You can on the category see there are more posts that shown on the map. 3 latest post didn’t register on the mashup