Academy needs 10% or less on the throttle, if it is not getting that it will not detect power off.
Have a check of the throttle. Pull the throttle back all the way to idle on your quadrant. In the cockpit, use your mouse on the throttle to see if it reduces any further. It is definitely either a miscalibration or something is restricting the throttle from moving back at its rest stop.
I’ll check the Honeycomb Throttle calibration, because I have similar problem with next lesson (Stalls & Dive). I guess it is close, but not exactly calibrated, because I have these problems… 
I mean, if idle is giving you more than 10% throttle input, I would argue it’s not “close” 
I don’t have the Bravo quadrant, but it looks like one of those with reverse on the same axis as forward thrust; I wonder if going full reverse would give you a completely idle throttle?
Regards,
Tim
Thanks Tim for your help. I already decided that I will remove all configuration from Honeycomb Throttle and configure the settings from scratch. I don’t know how this happened, but I feel that the configuration is wrong. And not necessarily just the single engine configuration. So it’s best to start from scratch, and not try to patch this together. It’s impossible to do PPL if the controller doesn’t work properly.
I already found a video that I thought I would follow:
