z series robot with E controller encoder problem

Hello Dears

we have two z series robots.
one of them fall in a problem.
the problem was :
(E1034) Encoder initialize error Jt 1)
I found that encoder or motor drive have problem.

I toke out encoder from the correct robot (that robot was OK)
and put it in damaged robot.
Now, i dont have E1034 Error but now i have
(E1123) speed error j1

I toke encoder out again and put it in OK (correct) robot,
Unfortunatly i have E1123 in correct robot,too

what i have to do?

note: i did not change motor with encoder
i only changed encoder.

Thanks for your kindly attention
It was for central retaining washer.