Validation for Required Field not Triggered until Data is Changed

In MDG-M, I have UIBBs containing required fields.  Some of the required field checks are performed by the Reuse area field control, and others are performed by my custom BRF+ Check rules.

PROBLEM: In a couple situations, the UIBB validation for the mandatory fields are not getting triggered unless other data within the same UIBB is first changed or new values are entered.

For example, in the standard Plant:Purchasing UIBB, the Purchasing Group is a required field. The field is marked as required in SPRO field control.  The validation message is displayed only if I first change some other field in the UIBB, such as checking the "Post to Insp. Stock" checkbox or entering the "Tax Indicator".

I also added a required field check in BRF+ for Purchasing Group as well, just to see how that would behave.  It has the same problem - it only is triggered after changing some data in the Plant:Purchasing UIBB and then re-clicking the Check button.

Here is a screenshot showing that the messages do not get displayed when I first click Check:

But after I change some data in the UIBB and click Check again, both of the validations get fired:

Any suggestions on how to get the validations to properly fire without requiring the user the change data in the UIBB would be greatly appreciated.

Thanks.

Rob