It shouldn't be that sensitive. If yours is a Android phone model double check you have the correct app installed for it, there are several that can show up in searches, mine is "Endoscope HD Camera" by Novotech Industries Limited. Failing that try it on a different device, if no joy you may have gotten a dud.Thank you! A great tip with the cartridge neck. It still looks like my camera is way too far focused. To get an in-focus image, I had to unscrew the mirror completely, and move it 1/2" away from the camera...
Or not... It might just went hyper-focal at this distance. Just how precise this adjustment have to be? A full rotation? 1/2? 1/4?