Hi Shane,
Here are a few details to help clarify:
I am running iFly on a Motorola XYboard 8.2 Android tablet, and my second device is a Motorola Droid Ultra.
I tested the tablet's manual brightness setting tonight and it smoothly goes from bright to dim with no problems.
I did additional testing just now, and the problem is actually a bit more insidious than I thought.  If I touch map mode, brightness,  and brighten screen, I can then set the brightness to anything from 100% to 10% without a problem.  If I then touch Darken Screen when at 10%, the tablet enters the endless standby cycle I described initially.  This is regardless of the Day/Night mode setting.  What I just discovered, is that if I don't first touch Brighten Screen the first time brightness is adjusted, and I instead go directly to Darken Screen, the tablet enters the endless standby cycle even if the screen is bright.  That suggests that simply imposing a minimum brightness setting within iFly will not completely resolve the behavior.
 
Knowing that this characteristic exists will allow me to deal with it while flying, but I just wanted you to know about it.  If you'd like, I can post/send you a video demonstrating the problem.
Thanks again,
Jim