It is in the node settings, so see if they are all coming from a particular node(s) and check the settings on the node(s) in ACP - Forums - Nodes. When you go into the node settings, look under Advanced Settings, there are options to Moderate New Threads and Moderate Replies. If you don't want a node moderated, they should be "off".
There is also a user/group right to bypass moderation. Maybe someone who should have that is missing it.