I have found this same issue. Normally trims work around the center of the stick travel. Ailerons, elevator and rudder work fine here. The throttle trim is only suppose to work at the bottom of the range. This would allow you to use the trim as an idle adjust needed for gas or nitro engines. After checking the DISPLAY screen I find that the throttle trim only works when the throttle is above the lowest stop and best when it is at center position. I feel this is a defect in the firmware. I have found a way around it but it is not the proper solution. Use the throttle curve at the normally set zero position and raise it up to 5 or 10%. This still allows you to use the throttle cut switch, (I use sw8) as a kill to zero. I have no faith in HobbyKing making the proper correction as I have posted this problem to their website and have got no response. This is not a problem for those who use electrics.