Reproducible with primary cells is an issue
If you are working on primary cells then you must understand that their behavior is very childish. If you treat them nicely and gently, they might grow unexpectedly. On the contrary, if you be harsh on them, it is possible that they become stubborn and won’t grow at all. With such nerdy cells, the reproducibility of results is often a challenge.
Read more:- https://kosheeka.com/things-that-we-still-dont-know-about-primary-cells/