This was a very good promotion, I booked a few stays in different cities. Today, I am looking at a funny EXPERIMENT:

A]
A question arose, to which I have not found an answer in Terms and Conditions.
I had booked during this promo and now that after the promotional period ended, I see that the room charge is now $25 lower.
What happens if I change the reservation to re-book under the lower price?
Will I still earn MQDs (although lower amount, of course)?

B]
OK... I am trying to change the reservation clicking on exactly the same room showing the lower price. When I click select, it says:

Something went wrong on our end

Sorry, your selection isn't available. Please try selecting other cancellation policy, extras, or a different room.

Fine -- I try to re-book the same room WITHOUT breakfast, the first screen tells me that the difference is - $40.

BREAKDOWN
$251 per night
Taxes & Fees $25
Local tax - Due at property $13

New total $289

Original total - $329

Total difference -$40

So, I expect I will get $40 refunded. I did exactly the same last year in Madrid and it worked fine.
Today, when I continue, IT WANTS TO CHARGE ME EXTRA!
On the next screen to be confirmed, it says:
ORIGINAL TRIP TOTAL: $328.56 (incl. taxes and fees, also incl. local tax payable in hotel)
NEW TRIP TOTAL: $306.50
Total Due Today: $15.53

Somehow it does not add. I know I was never good at math...