"ownersToDeeds" does not preserve previously owned asset.

[TEMHITHORPHE]

This particular line of code ownersToDeeds[msg.sender] = _deed; overwrites whatever was previously stored at that mapping, which means only a single deed/asset(the latest) is ever kept track of.

I think ownersToDeeds should be an array mapping instead:
mapping(address=>Deeds[]) public ownersToDeeds;

then ownersToDeeds[msg.sender] = _deed; becomes: ownersToDeeds[msg.sender].push(_deed);, this way, we append the list of owned deeds instead of overwriting it.

I think 😄