Could be as simple a fix as just working the elevator back & forth to get it freed up. Just disconnect the pushrod & flex the elevator up & down until it frees up. I just went thru a similar situation with a small electric. Thought I had a bad servo because it moved the aileron so slowly. So I took it apart & changed out the servo only to realize I had fixed the good wing.[>:] So I took it apart again & replaced the servo on the bad wing this time, only to get the same result. Finally the light bulb came on & I realized that I forgot to snap the hinge line after allowing the CA to dry. So I just spent a good bit of time working the aileron back & forth to break in the hinge line & now it works just fine.