is elevation screw tight? if loose problems can occur during assembly and disassembly
but sounds to me like the common stripping and jamming in the workings of the elevation knob/pinion shaft
in this case, new sights are in order, there's no way round it.
1/8th punch set on tip of pinion shaft in center of windage knob, and tap the shaft out
replace with usgi m14, m1 garand/bm59 or springfield m1a sights