Multiple Sub-grids on the same form hide form problem.

I am creating a wizard-like contact form where each tab in the form represents a step (Auto Generate Steps From Tabs is checked). I added metadata to the entity form to manage sub-grids so that I can let the user add new records to the sub-grids. 

Problem: whenever I have 2 sub-grids on the same form, the actions on the 2nd sub-grid aren't done properly (After submitting the form on the modal, the success message appears but the modal doesn't close to refresh the sub-grid).

Notes:

• The 1st sub-grid in the page actions work properly.
• The configurations for the forms shown when adding new records to the 2 grids are the same (Hide form on success is checked).
• Version 7.0

I wonder if there is a bug when having 2 sub-sub-grids on the same page.

Any help is appreciated.
Thank you.