Entity Metadata Wrapper error when editing sessions

So I can create sessions, and even edit them. However, if I set a Session Track and then come back to edit it I get hit with the following error:

EntityMetadataWrapperException: Invalid data value given. Be sure it matches the required data type and format. in EntityMetadataWrapper->set() (line 122 of /cod-7.x-2.0-beta2/profiles/cod/modules/contrib/entity/includes/entity.wrapper.inc).

I did a bit of debugging and the ->set() method is being passed an empty array, I'm just not sure by what.