I opened a bug report last week as suggested by Sparky Linden and got a quick reply. They seemed to have fixed the issue regarding the "Sorry to keep you waiting" message. Everything has been working fine for me now.
However, there are a few reports from other people regarding gifted items that are being delivered to the original buyer's "received items" instead of going to the intended person's account.
On a side note, a lot of people that I've asked, have never experienced any of these issues with the Market Place at all. So whatever the bug or error is, it just seems to be affecting different people at random times. I've seen older threads about that "Sorry to keep you waiting" message from 2012, 2014.
Anyway, feel free to add your comments to the bottom of the report to let them know if you're still having issues.