There is the obvious where patients have multi grafts, wrong angles, bad design etc that require repair work. Then there is poor yield which could fall into the category of a top up (a few hundred grafts) because there are some sparser areas or another surgery because the yield is way below. If the yield is way below, any underlying conditions should be ruled out. If there is no issues, then another surgery should rectify this.
There are some occurrences when a transplant will fail/yield poor growth for unknown reasons. This is referred to as the X factor in the industry. I don't know the percentage for this but at a guess I would say 1% or less going by online documented cases.
If you're uncomfortable posting your pictures, you could send them to other clinics for an assessment and report back what has been advised.