Quote Originally Posted by curious aardvark View Post
different filament ?
could be caused by inconsistent thickness in the filament I suppose.

You really don't see that very often these days - but it's possible.
Yes, I've tried different filament. I did a E steps calibration. Although I could not get it to extrude 100 mm, Somehow it improved the undextrusion issue. Just printed a calibration cube with zero gaps. But now the cube is .5 mm off in the dimensions. I might have slight overextrusion now. But at least the gap/holes are gone!