I can now count myself amongst the lucky Marriott members who were given difficulty applying FNAs to their reservations correctly when booking online.

I have 2 FNAs in my account - 85k expiring 2/2025, 35k expiring 10/2025.

I'm booking 2 nights at a hotel for next month which has a cost of 27k for Night 1 and 37k for Night 2. I get to the booking page and both FNAs are checked off to be used for the 2 nights. I obviously uncheck the 85k cert as I don't want to waste that on this stay. I thought that the 35k cert would then be applied to Night 2 = 37k points and I'd have to add a total of 29k points (27k for Night 1 plus 2k top-up). But no, the cert gets applied to night 1 and it asks me for an additional 37k for Night 2.

So I edit the reservation to book only Night 2 alone to use my 35k cert on that night. Now only my 85k certificate is showing which, I repeat, I am not going to be using for this. The 35k certificate is nowhere to be found.

Ok, so I used the idea mentioned here several times and book a random hotel for early February for 80k points and apply the 85k cert to that reservation to get it out of the way. Then I was able to go back and book my 37k room using the 35k cert plus 2k points and cancelled the booking that I used my 85k cert for.

Also booked Night 1 separately for 27k points. I hate being forced to have 2 separate reservations when I could have easily had both nights on a single reservation and that I had to jump through these hoops to use my 35k certificate.

Marriott IT at it's best.