No data for forum in subdirectory (2 replies)

I have Piwik installed and two "websites" connected.
Quotes used because it's actually one website (Wordpress) in the root and a Vanilla forum in a subdirectory, both on the same domain.

Data for the WP part looks fine and works as it should. The problem is with a forum part.

I got Piwik plugin installed for Vanilla forum and configured correctly. At least it appears so. The forum has at least 10 visitors at any time and about 10.000 pageviews a day, according to Vanilla's own statistics. That's a reasonable number and matches previous data before switching forum package (from phpbb).

However now it shows only about 10 (ten) pageviews and/or visitors per day?! Not zero, that's what bothers me. My IP is excluded from results.
Strange thing is that I have Google analytics code active on the forum simultaneously and it shows similar data.

So, my website (forum) works normally and plugin as well. Piwik obviously gets some data, but apparently only a fraction of it. I have no idea what to look for. My initial thought was misconfigured htaccess, but I'm not sure what part of it could block the data.

Any help is appreciated.

Added: Piwik v 1.12