Interestingly, there is evidence of pandemics of crystalin forms that contaminate whole laboratories and prevent the preparation of other polymorphs.
Take a look at Jack Dunitz and Joel Bernstein, Disappearing Polymorphs, Acc.Chem.Res. 1995, 28, 193-200.
I cannot avoid making this large quote:
1,2,3,4-Tetra-O-acetyl-beta-D-ribofuranose: The early history of this compound reads like a mistery history. As first prepared in 1946 in Cambridge, England, by Howard, Lythgoe, and Todd, the compound had melting point 58°C.
Virtually the same melting point was measured for material prepared by a different method in Jena by Bredereck and Hoepfner. When several batches of the same material were prepared soon afterward (1949) in a different laboratory on the other side of the Atlantic, in New York, by Davill, Brown, and Visser, the first three preparations had melting points 56-58°C, but the fourth run yielded material with a distinctly higher melting point, 85°C. Around the same time in Jena, by direct acetylation of ribose, Zinner obtained a mixture of two tetraacetyl derivatives, one the ribopyranose and the other the ribofuranose, with a melting point of 82°C for the latter. The two high-melting point compounds appeared to be identical, although the nature of the structurel difference between them and the low-melting form was unknown. So far, so good; innumerable examples of polyphormism are known. The low-melting form can be called A, the high-melting one B.
After some time, however, the melting points of the early New York preparations had risen to 85°C, and it was not longer possible to prepare the A form. A sample of A was sent from Cambridge, but when it was exposed to the air in New York, in a laboratory that contained samples of B, the crystals of A rapidly became opaque and transformed to B. In the meantime, transformation of A to B was also found to have taken place in Cambridge. Since the A form could no longer be obtained in the New York laboratory, further experiments involving this form were moved to distant Los Angeles, where it was shown that when 1 g of A (melting point 57°C) was inoculated with 1 mg of B (melting point 85°C), the melting point of the sample was raised to 75-77°C within 2 h and to 77-79°C overnight. Similar phenomena were observed in Manchester. Low-melting point A was first obtained, but when B was introduced in the laboratory, the whole of the material had the higher melting point and the low-melting form could no longer be prepared.
The saga continued in several laboratories and eventually it was not possible to prepare the A form, till 1981 when the rare A form was prepared again in a laboratory in Budapest.
At that time Budapest was behind the iron curtain, and it undoubtly prevented the contamination with the B form.
https://www.rhodium.ws