thats strange between me and 3 other guys we have about 38 servos and 18 of the 4 ch receviers, we haven't had a bad one in the bunch, you said you bought it on line, there is a lot of knock off's coming out of China being sold on E bay, you say chanel 3 doesn't work, a bad speed control will do what you are saying, also if you shouldn't hook up the servos to the tail and ele until they are centered by turning them on once, if they have never been plugged in they will be pulling all the way jerking and stuttering if you hook the ele and air on before pluging them in once so they are centered, Most dealers will take them back if you bought them from them if its in a 30 day period and take care of it, make sure the plug in's to the recevier are plugged in the right direction, all the white go one way and the blacks or browns go another, check and make sure the plugin's into the recevier are in tight also.
of all the electric stuff we bought we had one bad speed control out of about 60 piece's including all the receviers, servos'ESC etc.
I would go thru and replug in every thing , by the way if the radio wasn't on that will also cause the servo's to act eradic, doesn't make sense that you got 3 bad items out of 3