I assume proper hygiene to prevent post-implant infections, which would otherwise be the biggest risk.
Presumably the lab-grown hair needed some hormone(s) to stimulate its growth. There's a chance that this will also increase the risk of a tumour forming in one of the new follicles. If the hormone isn't properly washed off the new hair and finds its way into the body, it might also cause unwanted growth of hair, skin or other structures.
These risks are probably small but hard to quantify, and any tumour might take years to develop.
The removal and implanting processes will also involve some host cell proliferation to repair damage and provide a blood supply to the new follicles, and any cell proliferation brings a small increase in the risk of a tumour developing. In practice I doubt that would be significant, probably similar to the risk of developing cancer from getting multiple tattoos (which is somewhere between zero and miniscule).