It's not fully clear if the unintended yawing you have occurs when you try to use the same stick to ascend or descend or if it's just yawing with you not touching anything ... but never the less, looking into the flight log (.TXT) from such a flight will reveal if you have ghost rudder commands or not.
It's pretty common that the left stick will start to suffer of ghost rudder commands when trying to maneuver only the throttle to either ascend or descend ... this can be fixed by cleaning components inside the RC.
After a year of using my MA1 I started to get these annoying yaw movements when mostly trying to just descend/ascend ... it escalated to a silly level where I no longer could descend combining elevator for forward travel without turning off to another direction due to these ghost rudder inputs. The ghost inputs was clearly visible in the logs & also when trying to calibrate the sticks ... & couldn't get them to go away.
Then took the decision to break up my RC to clean them out ... followed attached YT vid ... pretty nerve wrecking to get it apart, took a good one & a half hours with leg stretches in between, but eventually I scored success without damaging some small plastic tab. No visible dirt, dust or debris ... but used alcohol & cleaned off the areas shown in the vid on both sticks, put everything together ... and problem solved.
It's pretty common that the left stick will start to suffer of ghost rudder commands when trying to maneuver only the throttle to either ascend or descend ... this can be fixed by cleaning components inside the RC.
After a year of using my MA1 I started to get these annoying yaw movements when mostly trying to just descend/ascend ... it escalated to a silly level where I no longer could descend combining elevator for forward travel without turning off to another direction due to these ghost rudder inputs. The ghost inputs was clearly visible in the logs & also when trying to calibrate the sticks ... & couldn't get them to go away.
Then took the decision to break up my RC to clean them out ... followed attached YT vid ... pretty nerve wrecking to get it apart, took a good one & a half hours with leg stretches in between, but eventually I scored success without damaging some small plastic tab. No visible dirt, dust or debris ... but used alcohol & cleaned off the areas shown in the vid on both sticks, put everything together ... and problem solved.