Data get overwritten in Goods Receipt PO

Hi, 

When I use Goods Receipt PO and write data in "Batch Attribute 1" and "Batch Attribute 2" the data gets deleted if I go from back in the felts again and data is deleted. 

 If I am in line 2 and use the arrow on the keyboard and go up, the data gets deleted. 

How can I change that?

Br

Jeppe