Sigh.... NONE of you should have to know the following....
There IS no MDE. The "system" consists of a front end Web site, slaved to old school Mainframes. SEVERAL of them.
This "system" is a hodgepodge of failing backend Data Base Systems circa 1980. The "Website" you see is lipstick on a pig.
When one ancient element goes south? The "System" croaks.
Now - Hotels. They each have their OWN local computer system, that tries desperately to talk to the MAIN system. This often fails.
That is why you can't get your MB to open your room lock.... but you CAN use it to pay at a Restaurant - even in a Hotel
. Front Desk? You will get the "OH! We need to REPROGRAM" line. This is the Front Desk kicking the main back end DB, yelling "HEY STUPID! WAKE UP!"
NEVER do this. It's a local HOTEL issue.
So - 99.9% of the issues you encounter have to do with MDE being a NON-BUSINESS WEBSITE. It is a mish-mosh of old mainframes, force-glued into something resembling a business website. It's a fake. MDE is a not-so-carefully crafted illusion, that likely drives whatever offshore WDW IT nuts.
WHAT to do? EVERY Reservation.... Room, Dining, Special Event? GET A CONFIRMATION NUMBER. PRINT that number, and carry it. That's for the next time this joke collapses. And it does so REGULARLY. You will note - AMAZON (a SERIOUS Business Website) never does this to you.
All personal opinion - I'm not necessarily right, no one else is necessarily wrong.