SEM-BCS Data Entry Layout - cell is blocked after input

Hello Experts,

I have a problem in SEM-BCS Data Entry Layout.

I have Account which is used for LC and also for transaction currency. First column is the amount in LC and the following 5 are for different Transaction currencies.

After my input on the account in the cell for LC and also a value for TC f.e. CHF and save the cell with the value in LC is no more open for data input and I can not change the values anymore. Just the values for the TC are changeable.

Have you an idea how can I fixed it? I wolud like to enter values for LC and TC for the Item but it does not work. Any solutions?

Thanks and best regards

Daniel