I found the difference between devnet and testnet. The NFTs minted using the same SC and endpoint:
- devnet: https://devnet-explorer.elrond.com/nfts/FFFF-364539-03
- testnet: https://testnet-explorer.elrond.com/nfts/RTYU-c271dc-15
The testnet is missing: 'attributes', 'uris', 'creator' fields. It looks like all which are ManagedBuffers, ManagedVec, ManagesAddress, etc.
Is this something on the api side? Smart Contract transactions executed without errors.