Update: Resolved. As long as I don't go to the Camera Settings in D-ViewCam, the Android app will continue to work correctly.
I've successfully added this camera to D-ViewCam via ONVIF. Works fine.
But when I go back to the "mydlink" Android app, it says "Another system is managing this device" and I cannot even view a video feed using the app. This happens even after removing the camera from D-ViewCam...
Interestingly, I can still view RTSP feeds: rtsp://admin:[pin]@[ip]:554/live/profile.0
Any ideas?