Nice that yours is working properly now :)
Good to know! I'll try some speed tests in future to see where the limits are.
But for now I think I just killed the poti for the extruder. I can't make it match the values of the other ones. It's overall resistance differs also.
I will have to order a new one.
I guess more soldering work for me ;) I might test the driver without any VREF resistor at all, when I have to desolder it anyway. Somewhere in the datasheet they say it is somewhat optional.