ME27 - vendor and supplying plant error

Dear Experts,

I am creating a S.T.O in me27  by giving input, supplying plant ABC,when i am putting abc as supplying plant,in ME27 screen showing me both vendor and supplying plant( EKKO-RESWK AND EKKO-LIFNR)

but when I am giving another plant xyz as supplying plant, I am getting only   supplying plant(ekko-reswk) not vendor (ekko-lifnr) in ME27 screen.

for both suppying plant using the document type ub and item category u.

please help me, thanks in advance

Message was edited by: Jürgen L