I ran into a new (to me) issue while booking a recent award redemption. Marriott applies award certificates inefficiently to charge a higher points co-pay.

I have free night certificates at different levels: a 35k certificate from a credit card, plus a 40k certificate from a 75-night choice award. I booked a two-night points stay. The two nights were 42k and 34k.

Applying the certificates efficiently would mean I would use my certs plus pay a 2k points top-up (40k cert + 2k for the first night, 35k cert for the second night). But when I applied both certificates to the reservation, Marriott would flip the order and apply them inefficiently: 35k cert + 7k points for the first night, 40k cert for the second night.

I tried different workarounds to get this to process correctly: unselecting the lower award and then reapplying it, same with the higher award, going through the pick-your-own cash and points option (choosing points each night).... Every time both certificates were on the reservation, though, it would default to the inefficient version. It was especially frustrating because when I selected just the 40k cert by itself, it would apply to the first night (the efficient way) and then would jump to the inefficient version only when I had both certificates live.

Has anyone else experienced this and does anyone know a workaround? Obviously there's always the option of booking two different reservations, but that comes with the (however low) risk of having to switch rooms partway through.

Thanks.