Also if tapping it works ( which it will ) you may want to adjust the linkages so that the control rod is connected to the INNER hole on the servo control horn. Then connect the clevis on the other side to either the middle or outer hole.

This gives the servo more leverage to move the control surfaces and give you finer control, but it will reduce travel a bit.

Since you are starting off, this will not be an issue at all, and you'll prefer the finer grain control.

BTW: My PTS planes also did the same think and as Miniflyer said, once the engine is running it stops.

As the hinges wear a little it will also stop.