Unable to Update Earning Item 1 in Payslips through Bulk Update

I took 2 payslips with different Earnings fields ( Earnings.1.Item) in the Batch Update Mode

I tried to copy Earnings.1.Item of one into the other, Both are in the key mode
when i pasted it back to update, it doesnt update

Is there a way to update Key Based Fields in Batch Update

As per the Screenshot, Im updating the Earnings.1.Item in the 2nd case
the transactions dont update