Error during back flush in MF42

Dear PP Experts

While doing backflush in MF42, I am encountering with an error and its desription is Account assignment object is blocked by user

Message RM183 , System error details says When backflushing for an account assignment object for first time, the post processing pointer table RESCO is adjusted, it is currently locked by user, You may also be locking in another seeeion.

This happens only for the first material in the list and it is not saying for the second material onwards during backflush in MF42/ MF42n

Any Idea on this please ?

Regards

PARAMESHWAR