This is bonkers. https://en.m.wikipedia.org/wiki/Disappearing_polymorphs Some pharmaceutical crystals can no longer be synthesised because they now spontaneously change to a more stable (but less medically efficacious) form. The more stable form acts as a seed crystal for the less stable form, and once this happens it creates a cascading effect, in which people who have ever worked with the stable form can contaminate an entire factory/lab and make it unable to reproduce the earlier form.