I remember talking to a friend who was doing a PhD in microbiology (implementing NAND gates in bacterial DNA) and she said reproducibility in chemistry/biology is a major pain. They couldn’t even reliably reproduce experiments within the same lab.

You’d have one postdoc do the pipetting and the experiment worked. Another person tried, following the same procedures with the same equipment in the same room at the same time of day in the same environment … experiment failed.

My takeaway was that a lot of this bio stuff is inherently flakey and/or poorly understood. We kinda mostly know what’s going but it’s really lots of trial and error and chasing statistical variations/effects. Best you can do is “it works N% of the time”