So, it's practically beating a dead horse at this point, but I noticed that we're actually running an old version of McMMO (currently on v1.5.08 SNAPSHOT). On Spigot, you can find v126.96.36.199, which may have some bugs fixed that the old version still has (i.e. Herbalism bug). Might be a good idea to update the plugin.
Link to the Spigot page: