First:
I suspected that u probly damaged the shaft, while removing the needle.
try to remove them again, but this time Push the needles back slowly, and gently.
To test it, just turn up ur needle and see if it drop back to zero freely and slowly without any hesistation?
Second:
Could be the overlay is not made of good quality, it might be not as smooth as OEM, cause it to not moving freely.
and If u have Not calibrate ur speedo needle, then u should calibrate it. Turn the needle clockwise, adjust so that the needle siting at ZERO.
thats all i could help,
cheers,
darrien