I think that means that you have 1 elevator half pluged into the wrong channel with the wrong mixing,,, if the regualar trim on your radio make only onw half move I bet you there is a dial you can move and will make the other half move too. and that is wrong you will have to plug one elevator half on the right channel so when you have the mix on the trim will make both elev. half move!!!!
REad you manual again and you might figure it out!!!!