Apparently the problem seemed solved by removing a custom code in the child theme but now the restriction of the coupon to an email does not work. This problem is also present in the base theme. I’d already tryed to deactivate child theme and activate Base theme in a staging website but the problem persists.
You can try in a wp stagin clone website.
I hope that you can help me to solve.

Hello, I have the same problem to saving data on all elements of sales booster.