It can happen that you are unable to save campaign/s for some businesses/merchant accounts.
You can try to create new test campaigns for the given business account/s and if you are able to save them, recommend to the customer to delete problem campaigns and create new ones.
Note: Don't forget to delete the test campaigns from the business/merchant accounts.
If the issue persists, contact support providing your Reseller Name and the affected business accounts names, and they will investigate and resolve it.
If the workaround does not serve the purpose, elevate the ticket to BU following the escalation path in the routing table.