I have one of these routers, the 3020 and found out that movements on all the axii had some missing steps as has been reported
on this forum.
So I decided to do the filter cap mods as described elsewhere here but found that didn't help a whole lot since I still had missing steps
and after doing some more searching here found another mod adding a Schmidt trigger inverter chip from the opto outputs for steps to the drivers.
After this mod was done I found one of the axis was no longer moving in both directions so I must have zapped that driver chip.
Rather than replace the chip I decided to take some of the advise here and replaced the driver PCB with a Gecko G540. WOW what an
improvement, no missing steps at all !
So because of the way the Chinese driver PCB was designed and not using the guidelines for that driver chip as presented by the chip maker
some that decide to make the mods may find it may not help and others feel it did the trick but my opinion is replace that POS driver
with the G540 you won't regret it.