Storage unit is already in storage bin & &

What causes this issue?

The storage unit number you entered already exists in the system or the
storage unit to which this number is assigned is stored in a different
storage bin than the one you entered.

How to fix this error?

Find out why the storage unit you specified already exists in another
bin. To help you do this, you should first display the storage unit
you entered and review the available data.
There are several possible causes for this error:

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

In your warehouse there are two storage units with the same storage
unit number.
In this case, simply assign a new storage unit number for the storage
unit found.
According to the system data, the storage unit you found should be
stored in another bin. It is possible that the storage unit was stored
in the wrong bin by mistake.
In this case, assign a new storage unit number for the storage unit
found. In this way, you ensure that the stock data for the storage bin
where you found the storage unit are correct.
Afterwards, you must ensure that the stock data for the storage bin
where the storage unit should be stored are also correct. To do this,
execute an inventory for the bin concerned and enter <LS>0</> as the
result.
Also make sure that the storage unit you have found and for which you
have now assigned a new number is also marked physically with the new
number.

Error message extract from SAP system. Copyright SAP SE.