Unable to schedule report with optional prompt

Hello Experts,

Environment:

BusinessObjects 4.1 SP5 Patch 4

Report created on Web intelligence

Source:  Bex query using BICS connection

Issue: Unable to schedule Webi report which has optional prompt defined in bex query.

Problem Statement:

When I try to schedule report with optional prompt it does not schedule and return error during definition "An internal error occurred while calling 'answerPromptEx' API. (Error: ERR_WIS_30270)"

Strange behavior is that report runs fine in BI launch pad with or without prompt value.

I have checked report to see if any of the underlying dataprovider has mandatory prompt but found all data provider are with optional prompt only. Even I have many other reports have similar configuration which are working fine even in scheduling.

Please help me to know what could be the other reason for this error.

Thanks in Advance,

Priyank Bhayani