I am having bottom tension issues on a couple of Juki DLN 9010A-SH...one brand new machine and another that is only about 8 months used.  The issue is bad tension on the underside of the fabric only when the machine is doing a reverse stitch using either the reverse lever or the reverse button.  Tension is great when sewing forward. 
 
	
		Things that I have checked adjusted, re-adjusted, tweaked, changed you name it:
	 
	
		Machine head properly threaded
	 
	
		Brand new needle size 18, installed correctly
	 
	
		Bobbin tension
	 
	
		Burs on hook
	 
	
		Needle & hook timing
	 
	
		Check spring tension
	 
	
		Presser foot tension
	 
	
		Feed dog height and positioning
	 
	
		Put new feed dog and needle plate on
	 
	
		Tried different presser feet
	 
	
		Measured forward and reverse stitch length which both came out equal
	 
	
		 
	 
	
		Am I missing something or is there a problem much deeper in the machine?