Just in case anyone cares (I doubt it):, the bug still exists on wheezy, same test case and basically the same patch (attached) as on squeeze.
5 successive tests failed within 90s each without the patch, 5 successive tests did not fail for >120s each with the patch, so it seems even better reproducible than before, or it's just my slightly different environment now.
jack-watchdog.patch
Description: Binary data
