I am sure i am not the only one to experience this bug/issue.
The problem when in Admin view or Classic UX:
When scrolling to the bottom of a module (one large enough to require scrolling to see the line items at the bottom of the module) the bottom-most line items can not be reached using the scroll bar. To even see these line items you must select a visible line item and use the down arrow keys to reach the bottom-most line items. It looks like the auto-calculate bar which appears automatically is causing the issue.
The solution: Allow the scroll bar to reach the bottom-most line items such that ALL line items are visible.