I have been experiencing something similar. I believe it started with the latest update of the Explorer app (on Android). At the beginning of a flight, the click doesn't occur when pressing the shutter button on the controller. I don't think that the thumbnail of the photo shows up, either, so I'm still not certain whether the photo is actually being taken. After going into the camera settings menu on the app (the strip at the bottom of the screen) and back out again, the click and other aspects of photo taking started working again. This occurred on each of several flights last week.
There also seemed to be some difficulty with accessing the camera settings, but I eventually got it to work. I suspect a bug with this version of Explorer. I may submit a report shortly.