Command-and-control managers think their job is to ‘manage’ suppliers and they do so with contracts, service-level-agreements, service standards, job/price schedules and so on. These conventions drive costs up and for the long term.
Suppliers are part of your system and should be treated that way.
The fastest way to change from conventional supplier management to treating the supplier as part of the system is for both parties to invest time in understanding and improving the system. While that is going on you put the contracts (and the lawyers) in a drawer.
Once you have a better and stable system you can discuss any requirements for a contract.