Timesheet hours reverts to zero

Issue: When attempting to add “hours” to a timesheet entry in the timesheet detail entry, the hours revert back to zero, whether entering directly in the hours field, or selecting an end time. When entering hours in the hours field, it appropriately adjusts the end time, but then the hours reverts to 0. This causes the system to not add time, nor can timesheets be submitted.

However, if the “Timer” function is employed, the time is properly submitted and the hours stay populated.
can anyone help me to solve this issue?

Noted here too and issue reported thanks Timesheet Hours only work with Timer Feature (v11) when "Standard Working Hours" Set