Defined field is too small error in qas

Dear all ,

I am getting defined field is too small in qas server but in dev im not getting any error ,, error showing me problem is with 'move' statement,

Run time error:

          loop at itab to wa_tab.

>>>>>>>>move  corresponding wa_tab to wa_tab2.

in wa_tab i have field itemno type DEC length 8 decimal places 3 .

in wa_tab2 the same field have type P decimals 3 ,,,,,, is this a reason for a dumb ???

if yes , why there is no dumb in DEV server.

itab have 160 line items for first five line items there is no dumb that  i have debugged . dumb coming only after some line items

Thanks