Ok, ran more intensive tests.
It does not seem to loose the defined detection zone, it just seems to not read it properly after a specific sequence of events within the application. Not 100% sure if this has an effect on the motion detection events generated.
For instance, I click the detection zone and it shows the full window as being defined, which should not be. I hit the back key without changing anything, go back in the detection zone and now the detection zone is properly set. Will it use the full window or the defined area to generate motion events? Have no idea for sure. Therefore, I will make sure that the defined area is set when I leave the detection zone screen setting, instead of the full window.
It seems to be triggered when the thumbnail picture of one of the cameras on the home screen gets updated and also seems to be specific to V1 only. I have a mix of V1 and V2 cameras.
Should probably change my V1 cams at some point however I find the picture to be as good (if not better) than the V2 cams (not as blurry and better KB/s when tested at the same distance from the router. This is especially noticeable in lower light conditions. Not talking night vision here.). Also, the V1 cams do not have the out of sync audio that the V2 is experiencing.