First 15GX2 was replaced for the same reason, the throttle barrel is binding when being opened or closed.

They replaced the first engine, sent me a second and it is also binding. Called Horizon Hobby and they said to send it in again. Getting a little frustrated. Just finished building my Sig 4 Star and was at the field to break it in and throttle started to bind. Worked just fine at home when I set it up, but as soon as I started it, the binding occurred.

Any ideas why it would bind? I disconnected the throttle cable and pushed the throttle arm with my finger and could feel it hooking up.