Intermittent posting to wall - sometimes not

The plugin is working great, however every now and again it seems to skip posting to the wall. I'm not sure if it's a common thread (e.g. a specific category or author) that does this, but it seems to happen randomly.

You can see all the posts made to our wall here: and then the actual posts are here:

the posts on the wall are all made by the Between 10 and 5 application.

Is anyone else experiencing this problem?