Controlling a servo through an auxiliary output on QGC

Hi, as a beginner I am struggling to figure out how to control a servo through an auxiliary output on QGC. In my case, I put a servo on AUX1 and also set RC_MAP_AUX1 parameter to Channel 5 but it didn’t work. Except this one, I have no problems controlling other servos connected to main out and everything works fine.

My airframe is standart plane. Does the aux mix of this airframe cause such kind of a problem? Or, what else might be causing that? Any help would be appreciated.