I bought 3 of these little things for presents last year. Like the Vertibird replica I bought my nephew the year before I felt obligated to put the whole system through a rigorous flight test and evaluation regime before I deemed it acceptable for use and ready for customer delivery.
I too noticed the strange ceiling effect. It was often somewhat like watching a cranefly repeatedly bash itself into the ceiling. I found that to pull myself out of this effect I had to drop power quite drmatically, and the descent once out of ICE was too great to recover from.
Strangely, and despite the pilots best efforts (honest), I found they are also magically attracted to cats, for which they are no match. My 4' Maine Coon took great delight in whacking it out the air and pouncing on it before picking it up in his mouth and running off through the cat flap and into the garden with it. I also learnt that they have a decidely negative impact on female temperament during Christmas dinner.
Si