Glad you found the issue.
The rudder will definitely sap your planes energy.
Auto trim, or auto pilot (lvl, climb, speed) should properly position the control surfaces for a given flight envelope. Unless there is a control input, intentional, or not. That will kick it out of auto pilot.
You can check your controllers fidelity by checking the advanced box under map controllers, then selecting the axis you want to look at. The green line should be fairly steady in the middle of the window until you move that axis. If it jumps around or is towards the top or bottom of the window with no controller input then you have a calibration, or hardware issue.
