After a crash, I noticed that one of my servos is not moving as far as it should. If I pull up or down on the controller, the right control surface only travels about half as far as the other one. Yes, my tail was all centered up the way it should be.

When the trims and controls are centered, the servo arms should be about 90 degrees to the tail. Something like the picture. If not, it is possible one of the servo arms has shifted. If that is the case you will have to remove the control board to fix it.

If that is not it, then the sero may be damaged. You will have to buy a new fuselage. about $42.

Photos are from an original Aerobird, not the challenger, but you should be able to get the idea just the same.

one easy thing to check as well...before removing the controller board that is..... did the controller board itself come loose from a crash? the board is anchored to a plastic bracket that screws into the bottom of the fuselage. I had mine break loose from impact and noticed the same control response you are describing. careful, as well as not so careful, epoxying and I was back in the sky. Unfortunately mine got to the point that I actually have epoxied my controller board to my fuselage. Means I can't do some of the differnt control mods out there...like piano wire and such. My new fuse will be different though. Enjoy!