Thank you for reaching out!
The option “hide RG scroll bar if nothing to scroll” have to work only when the repeating group has no data to show. Unfortunately, we found observed a bug, the option is not hiding the scrollbar even if there are no data in the RG. Our team will check the issue and once it will be fixed I will let you know.
Regarding the issue, which you reported in the private message. The error “Syntax error, unrecognized expression: #” appears when the field “Element IDs to apply custom scroll bar” from the Custom scroll bar element or action is empty. Please make sure you specify the element IDs and the error will be fixed.