Thanks for these helpful informations and solution!!
I found it when I was completely desperate as I didn’t manage to move the Kodiak 100 Amphibian on the ground at all when starting from cold and dark! No power, no idea how I could move that plane. Your answers showed me that it’s no bug but I am just to stupid to handle the plane correctly… 
Today I found the following video and it solved all my problems!
just start up as shown in Jonathan Beckett’s video and you get full power available - with Stick-Calibration (switch reverse thrust) I am now also independent from pushback service… 
I thought it might help other people like me, so I post this link:
