I have assisted in many pre-clinical and clinical research opportunities to know a lot of the ways that it can go wrong. I specifically worked with rats and performing surgery to remove their brain and basically freeze them in a certain preservative in order to transfer them to other places or just store them for future use. However, a lot of the times, the brains would not correctly be placed in the preservative, basically making the brain useless to use. Sometimes it could be a malfunction with the equipment, such as the freezer. If the freezer stops working overnight, it can be a problem going back to work and realizing that all the samples are unviable. There has also been times where the rat was improperly disposed leading to regulatory failure. There are also times where protocols are not exactly followed and corners are cut in order to speed up the process, which can lead to false data.