Scenario:
User is able to select and enter time against the disabled client which was associated with bucket method project. Let’s assume that you have following clients associated with Project A which is bucket method,

Client 1
Client 2
Client 3

Disable Client 1 and it gets removed from the client list associated with Project A however, it allows users to selects Client 1 on timesheet and also allows to enter time against Project A. When you disable one of the clients associated in a bucket method project, it should not allow user to enter time against the project when he selects the disabled client.

Resolution:
Switch to the new smart interface with Standard 2.0 timesheet format, as this behavior has been fixed. The old Standard timesheet format won't efficiently update with this new functionality.