3818214 - Why alerts come out "The report has been saved, but it is still missing information that is required before it can be submitted. Would you like to add that now?"

There's an issue in our test and prod environments：

When creating expense report，filling all mandatory fields in report header，there's an red alert： The report has been saved, but it is still missing information that is required before it can be submitted. Would you like to add that now?

After selecting no，the red alert disappear.
The issue can be reproduced in any account in Concur test environment.

hidden field is set required but no default value set to it , KBA , CON-EXP-ADM-FOF , Forms and Fields , Problem