Sorry, I meant I’d like to see your shortcode with “posts_per_page” in it, since I didn’t see any query in that shortcode.
If you use the mashup shortcode with no query, the plugin will try to show all posts.
If you use a query in the shortcode you can limit which posts are searched and limit the number of results.
There are some examples in the documentation, but basically you could use something like this:
[mashup show="query" show_query="posts_per_page=-1&post_type=any"]
That query will search ALL posts so you might want to also specify a category or tag to limit which posts are checked for maps.