Of these 3 encounters, #2 (failing to honor a room configuration for a group in 1 large suite, which includes children) - is inexcusable. A much larger group, multiple rooms and some kind of requirement they ALL be connected can fold the stay plan if one or more of the rooms is down for repairs. Hard to accommodate that large group but knowing your small group had minors - they should have had a better solution.

#1 (stay credit) happens from time to time but unless the points are critical for a Reward stay or something, it's just annoying.

#3 (the dreaded rate change) has been an issue for me, but not in core Marriott properties in the US because I expected it. When I've straggled a stay on a long trip 2 more days to relax over the weekend, then decide to leave early Monday, the rate often changes and that's made clear.

OTOH my last stay for business during the week in the FRA Marriott had to be moved up 2 weeks, but I had the same rate. The added 2 days (Sa/Su nonrefundable) took some doing to change to leaving on Monday. On checkout the staff gave me a rate break credit that applied for those 2 days because their current offering, even leaving on the start of a business week was cheaper. So it works both ways sometimes1.

If the Autograph staff made a mistake - it's a mistake. If it was fixed, let it go. If they had not taken care of it & you had to eat the higher last day rate at least one more one option exists: If you billed on AMEX, particularly GLD or PLT, they are pretty good about crediting part or all of disputed charges for a miscommunication by one of its merchants. Some other cards may do this too, but AMEX is very responsive.