I THINK your problem is using two channels for elevators and reversing one of the channels for one elevator. If you drive BOTH elevators from the same channel and then, on the SERVO page, reverse the required elevator servo you MAY find the problem solved.

Then repeat position and end point learning for each function.

This is only a suggestion as I do not have a Pioneer, my standard is the Competition SR 2, but give it a try !

My experience with the I gyro is that it is an incredibly capable device based on 4 I have in service with 3 others about to be installed, attitude assist on ailerons is awesome.

Another tip: On my latest install, BVM F 4 with Xicoy 180, I ganged 9 ch and 8 ch receivers. Not sure why ( it will be changed this weekend) but Rudder is assigned to the 8 ch receiver. That does not work , the gyro can control ONLY functions on the 9 ch, ie receiver with fast track to which the gyro is connected.