Ive had that juddering and can't rememeber what caused it
but it was usually when I stopped moving the sticks. The servo would respond normally then when I returned the stick to zero it would judder like that.
Also had something similar recently with my Tiny cub, it was fine on low rates but on high rates one aileron started twitching. It flew fine on low rates but didnt trust it so swapped over the receiver (FRsky TFR6) and my old Futaba. I connected a new Radiomaster R86C and my TX16s the problem went and now it works fine on all rates.
Are you on 11ms or 22ms repsonse for the receiver type ie DSMX 22ms ?
Also check your not on a low power setting on the TX
Finally check to see if they are both anolouge or one is digital servos ?
Trying to think of something obscure now that might be affecting it.
Try connecting a 4.8v supply to the receiver direct rather than through the ESC and lipo etc see if that has an impact.
Sorry struggling a bit now with options.