RentalFeeAmount is a fully additive measure.

The fact table would be consumed within a view to provide the most recent record version at the reporting date and it is the view that gets rolled up on the dimensional values.

So the when the view is run with a March date, the first copy of the record is provided, and any view date for April onwards would give the second copy of the record. In this respect the change to the dimensional surrogate key would be treated no differently from a change in a real fact (e.g. the customer had traded in the original 'camera' item for a completely different 'electronics' item but still on the same terms and agreement number.