OK, so another possibility at this point is checking in with MapPress’s support team and seeing if they have any ideas as to the cause; right now though this is really looking like an integration issue between the two plugins that you, or the developer handling the integration (if you are using a developer), would need to solve.
With that said, if it does turn out there is some sort of malpractice or something we could do better in our code to ease integration definitely let us know and we’ll happily look into making a change.