Ok, in lieu of a screenshot what is being changed (specifics) and which spell you are casting, and which button you are using to cast it would help. Note: there are multiple (2-3) buttons to cast any given spell, which is why we need to know the button specifics. Also, knowing exactly what is being changed can help try to reproduce this as there are multiple ways to affect the Spellcasting Ability and the Spell Save DC.