There are a few audio-using APIs from Apple that you can’t run simultaneously with OpenEars (or other 3rd-party audio frameworks) because they need to override the required audio session settings for the other framework. That’s an expected result since the design of iOS is a singular audio session with overridable settings. In this case the Apple framework is changing the session settings that OpenEars needs, and in one case it prevents recording (but it sounds like it is doing well under most circumstances).
(Since both frameworks are not open source, I can’t solve it at low level neither).
You can make changes to your copy of the OpenEars source if you want to change its audio session behavior.