Hi, Sorry for no reply yesterday. Can I ask a few questions please...
What is the thickest material you have stitched? Will it cope with 1/2" of veg tan leather?
Can you set your servo motor slow enough to easily control stitches one at a time?
Does it ever skip stitches?
I see there has been lots of wear on the foot you replaced; knowing that it is an expensive part, my concern would be that the hook may be quite worn too; have you replaced it?
Do you have many of the larger bobbins that the machine uses?