When I start the Android app, wait for the GPS to be found (Green status), presse the start button and then put the screen to sleep with the power button, the activité is well recorded.
But if the GPS is not found or weak when I press de start button and then the power button, the activité is not recorded until I wake the screen, which is often when I finish the activity (happens mostly when I am commuting because of the topography).
Its happens more since the latest update of the recording interface, a few weeks ago.