How to solve this issue ?

Hi,
Looking at your screenshot, it's a bit unusual to have similar entities (Unit1, Unit2 and Unit3) all part of the same record rather than 3 discrete records and I would guess this is the cause of your issue, but it's a simple enough fix. 
Can you attach your project (zip up everything except the .exe).
Then someone will be able to take a look and suggest fixes or alternative approaches.
Regards,
Derek.

Hi,
The problem you have is because you have 4 relationships between the 'items' and the 'units' tables.  MVD will only automatically retrieve the unit_name for the first of the relationships.  For the other 3 relationships (the sales units), you have to do this manually.  This is done by adding calculated fields in the database tables.  Have a look at the attachment (Items_Option1) for an idea how this is done.
As I mentioned previously, it's a bit unusual to have similar entities (the 3 repeats of sales items) on the same record.  To see a different approach, have a look at the attachment (Items_Option2).
Neither approach is 'right' or 'wrong' - it's more a matter of 'horses for courses' and underlines the flexibility of MVD.
Regards,
Derek.