Problem when error message in exit Save document prepare(MV50AFZ1) on PGI

Hi,

I am using USER_EXIT_DOCUMENT_PREPARE for throwing error message during PGI. The error triggers properly, But after that if I press enter button, The program ends with an ABEND error 'Risk of posting several mat.documents for one delivery->long text'.

If anyone come across with this please help me.

Thanks in Adv.

Regards

Nishad