Poor man DRO

Sometime ago i have find a site with the subject of making a DRO
using a mouse and software (encode5) for dos.
After some testing it seems to be ok, and i start to built some
gearing mechanism to give me 0,1 mm accuracy (divide that with the
quadrature sensors final res was 0,025mm.
but after instalation the y axis worked fine the x axis sometimes
worked sometimes not,i have test 6 different mouse and i get more
wierd results if i turn the handwheel fast is accurate but if i turn
it slow it misses.Any suggestions?
I have solder the sensors with a 25 cm cable from the original pcb,
the cable is from a mouse, i made the encoder wheels but to the same
dimensions as the smaller one found in a mouse.
I have aligned the sensors perfectly.