Unfortunately the “decoder.output_projection.weight” param is not zero at all, as you can see it here:
mbart-fairseq-011206×143 28.5 KB
Probably it is the same as decoder.embed_tokens.weight acording to https://github.com/pytorch/fairseq/blob/522c76ba1646cd5ec2cd4be29392f53d40aec50a/fairseq/models/transformer.py#L627 12