This strange chars just before the X: 
Expand the inspector panel and you will see it’s the beginning of (Using Quaternion)
While you are try to use euler angles in your code.
.GLB files are loaded by default with Quaternion.
In the onSuccess callback of the load, add this on your mesh :
let rotation = mesh.rotationQuaternion.toEulerAngles();
mesh.rotationQuaternion = null;
mesh.rotation = rotation;
Then setting up the rotation using .rotation.x , rotation.y etc… Will work 
++
Tricotou