I just built my flitetest tutor. This is my first plane. I'm not sure what I've done wrong. I'm using a radio Master tx16s MK2 transmitter with the radiomaster r88 receiver. It seems to be receiving signals properly and the transmitter is showing the proper gradient as I move the throttle. However, plane motor seems to have three stages of throttle. When I hit 34%, it drops back down to low throttle and starts again moving up in speed till it hits 66%. Then it goes back down and starts back up again. Does anybody have any recommendations on where to look so I can correct this problem?