Recently, I have faced issues where clients put less money than agreed in the escrow and then go silent post receiving work. If I send reminders, they come back with some flimsy excuse to not pay. Happenned with an agency/client called **Edited for Community Guidelines**. They stopped responding and are not releasing my payment.
If you submitted the work using the »sumbit work » button, the client has 14 days to review. If he doesn't do anything and Upwork can charge their payment method, you will get the amount on the 15th day, then after a security period of 5 days.
If you send the work for the lesser amount of the milestone, this is the amount you will be paid. You should only start working when the amount you agreed to is in escrow.
Of something goes wrong with payment, it is the freelancer's fault.
If the client funds $10, the freelancer should do $10 worth of work.
This isn't complicated.