I have been having print quality issues and have done everything I can think of to solve it. New nozzles, different extrusion temperatures, new extruder gears etc, etc...

In the event I had a look at the motherboard and changed the A4988 drivers round, but no difference. Then I installed new drivers and in doing so I moved the wires in the crimped connector for the extruder cable and one wire just came out, so I took out the insert and soldered the wire on, reassembled and tested.

The problem was solved - print quality back to normal.

So I reckon it was missing steps and not pushing the filament through evenly due to a poor connection, which was either intermmittent,high resistance or both.

Broken wires to steppers seems to be the most frequent answer to problems on this forum. That I can understand with a lot of constructers, but this was a manufactured cable.