Mar 19, 2021 04:02:36 AM by Ali T
Mar 19, 2021 05:18:06 AM by Will L
Upwork doesn't care whether you and your client agree to change your contract from fixed price to hourly as long as all payments to you are processed through Upwork.
Take payment on your Milestone 1, have the client cancel the project and leave you feedback, then start a new contract on an hourly basis.