Mould growth on frozen chicken

Mould growth on frozen chicken Hi all, we have frozen whole imported chicken stored at -18 to -22oC, the chickens are within shelf life dates and proper storage requirements. However, we noticed mould spots on it. The moulds range from black spots to fully grown moulds. What are the main causes of this?

media shows chickens was not frozen properly.

That would be from the initial stage of post processing?

Freezing process was not applied as required or the cold chain was broken.