Case
In transaction MR21 in order to change the price of a material in a sales order you select the variant ‘MR21_ALLE_MATERIALIEN_BMKEY_02’.
After entering the new price and executing the currency conversion, the program displays the error message M8 782 (Internal error (read error SMBEW, key = &)) as you save.
Solution
WARNING: This is an IS-OIL / IS-MINE-specific note !!!
Due to program error the fields VBELN and POSNR are not filled into SGNBU structure.
Apply the solution in note 2106691