RE: Project locked during timesheet approval
During the time of posting of the Employee Time Calendar, if any of the project related screens are opened then the Employee Time Calendar will be struck and also Customer Project Expense List will also be struck.
This could only be temporary issue.
Can you please check in the General ledger > Source Documents > Unposted Source Document and try to find this Employee Time Calendar & relevant Customer Project Expense list of it, are they showing as Finished ? are pending .