AP 3.8 elevon/servo/rc mapping issues

Hello all. I have been flying an older apm2.5 board in a delta wing with AP 3.8. I have been running mission planner 1.3.48 for a little while. I recently migrated from elevon mixing on my RC to elevon mixing on the APM. This was a little hard to sort out but I was ultimately successful.

I am now attempting to set up a pixracer running AP 3.8 on the same delta wing with elevons, and I am having a very difficult time separating servo reverse functions from rc input reverse.

An example. When I set SERVO1_FUNCTION to 77 (left elevon) and SERVO2_FUNCTION to 78 (right elevon) and both SERVO1_REVERSE and SERVO2_REVERSE states are both set to 0 (disabled), i can check pitch and roll inputs on the radio calibration and both are normal. When I change either SERVO1_REVERSE or SERVO2_REVERSE to to state 1 (reverse) , pitch and roll channels on the radio calibration page will reverse without any input on my part.

Worth noting that I am attempting to stand up a taranis x7 and an Sbus rx with this pixracer, while my previous APM 2.5 setup was running a spektrum pwm input. Hard to see why this should be an issue, but want to put all the variables out there.

I am running a seperate instance of mission planner 1.3.48 and APM 3.8 on a pixhawk mini with a spextrum satellite rx and I don’t see the same behavior.

Main question, is this a pixracer issue or some setting i may have overlooked in mission planner? or is this something new related to SBUS?

Any help would be greatly appreciated.