In the current implementation of CollateralToken#onERC721Received, _mint is used instead of _safeMint, _safeMint checks that if the recipient is a contract, the receiver implements the onERC721Received hook to acknowledge that the contract is capable of receiving NFT to avoid loss of NFT ownership, however there is no such check in _mint, result in loss of NFT if the recipient is not designed to receive NFT.
We recommend the protocol use _safeMint instead of _mint when minting collateral token.
