Bukobot Duo failed extruders

[lockbot]

I have had my bukobot since February. This is a 3.0 mm filament with a .35 nozzle. I have had very few good prints. After a while the extruder starts slipping and does not extrude. Thus print failure.
Both PLA and ABS usually starts off fine. I can manual feed from repieter host all day long. I have tried to print with the MicroSD card, and from USB.
I have spent hours and hours changing extruder temps, measuring and measuring again filament diameters. I have 3 or 4 filament manufactures product.
I purchased a MK8 on ebay with no luck. I have swapped out the stepper driver to the extruder, I have added a fan to the stepper driver, and changed the fan to the extruder to a more powerful one.
But after a while the filament starts to slip and not feed. I can watch the extruder gear dig into the filament.
The nozzle is not jammed. And the failure could be at layer 1 or 25 doesn't matter.

Does any one have any suggestions? I just want to print good parts.

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