depends on which surface the rudder and elevator or the ailerons? my NEXTAR had a problem with the ailerons, they loosened up at the torsion rods, they were not glued in and had loosened up allot,caught them just in time I had to channel out the wood around the wire and filled the void with 5 min. epoxy, since then they have been rock solid.
the 3003 servos aren't that bad the 3004 are ball bering are a little better they are the ones I use in all of my other models if you are able to move the control horn without hearing the motor sound there is some slop either a gear has worn or the teeth are worn or worse broken, REPLACE asap the 3004 servos run about 12 $ the 3003s that came with mine are still in great shape, unless they are broke or super loose save the $ , if they are broken and you are not comfortable changing gears in a servo just buy a new one of course. also the push rods are not exactly stiff or anything prettty weak if you ask me they have a little flex in them for sure.
once trimmed the NEXTAR should fly its self you should not have to touch the trims for the most part the thing floats like a balloon