"A reproducibility crisis is a situation where many scientific studies cannot be reproduced. Inappropriate practices of science, such as HARKing, p-hacking, and selective reporting of positive results, have been suggested as causes of irreproducibility. "
Also, lack of raw data or data fabrication is another possible cause of irreproducibility. Here is a paper named "No raw data, no science: another possible source of the reproducibility crisis", which helps us to realize that lack of raw data or data fabrication is another possible cause of irreproducibility.
(https://link.springer.com/article/10.1186/s13041-020-0552-2)