I've been having problems with the V5.4.20 app on my Android phone. Sometimes it seemed to hang while ending a recording. Other times it seemed to hang when manipulating the lines I had drawn (moving them around) during playback. On one occasion it recovered after a couple minutes. Other times I I couldn't even end the program and had to restart my phone Trying to recreate the problem, I opened a video file, pressed Play, and then tried to use the >>> button. The progress dot snapped to the end of the progress line, and the screen froze for several minutes, then turned black for a minute or two, then reappeared. And now it works OK!