Clicking the background Commits the layout's record just like the Commit Records script step, so I am surprised that commit records was not all that you needed to get the other portals to update.
You might try Refresh window either by itself or in combination with Commit Records.
Commit records or with the last 2 reversed fail to remove the records from the portal.....only the physical click does it. So yes, puzzling!
try refresh window with the flush cached join results option. While that may not be the best final option, if that version of refresh window works, it will tell us something about where the issue may lie.
And are you actually deleting the child/grandchild records via a cascading delete or does deleting the "parent" portal record simply remove the link to those records?
I really don't want to have to confess this........but I'd not assigned the script correctly to the button.........as in not at all !!!
Delete row & Commit records steps are sufficient script steps to remove the parent portal row and, because relationships permit deletion of child/ grandchild portal rows both they and their respective records are deleted.