Yeah I don't have a problem with liens, I have a problem with unregistered liens. There needs to be a system for registering and searching liens, it needs to be publicly accessible and the lien needs to be registered before it's valid. In order to register a lien on a car you need the owner's signature, that can't work when the owner has changed. Mechanic needs to get the contract signed then report the new lien to wherever it should be reported, and once that's all in order they can start working on the vehicle.

If they try to register their lien once the owner of the vehicle has changed, it can not be accepted. You can't secure debt with a vehicle you no longer own. The lender needs to make sure the person owns the car and register the debt while they still own the car. And if they sell the car then they have money to pay the debt, and since they no longer own the car then their debt is no longer secured so that should trigger a requirement to pay the debt per the loan contract. Debt should be owned by people not objects.

The whole concept of debt that's attached to objects is silly. It can make sense in certain situations like a housing association that's taking up a shared loan and paying it down as part of shared monthly expenses, but for a car repair or similar it makes no sense. The person who takes the debt is responsible for the debt. If they sell the car then they pay the debt with the money from the sale, if the sale doesn't cover the debt then they still owe the rest.

It does not need to be any more complicated than this. In order for anyone to take over responsibility for debt in relation to a purchase, there needs to be explicit written and signed consent. So - I can buy a house including some debt if I know and agree to it, but I can't unwittingly buy a landmine. If the owner fails to resolve their debts when they sell that should be their problem not the buyer's. It's up to the bank to collect their debts from the person they have a contract with.