My spv node received in a nTx = 2 in headers message
I have found what I was missing.

Dogecoin switch to merged mining so the header has a new structure which I didn't know about. I found this wikipedia page (https://en.bitcoin.it/wiki/Merged_mining_specification#Merkle_Branch) which explain everything.

I should have noticed also that my nonce is 0. When I see this and that the next bit is not null I can extend my structure to a merged mining header.

I hope it will help people.