You may find it was a weaker graft that just takes longer to respond. The hairs grow in cycles, it may grow fine and wispy where you don’t really see it, then sheds and grows back stronger.
Like how a plant may grown, you move it and it may wilt and look half dead, then over time it recovers, same type of thing with grafts.
Some go through more trauma than others, some are stronger etc.
This link explains it in more detail.
Great strides have been made in hair restoration over the past 20 years. A better understanding of natural balding and non-balding patterns along with more respect for ageing has helped guide proper hairline design. Additionally, the use of smaller grafts ...
www.ncbi.nlm.nih.gov