Actually just contacted Amazon about the whole Sunday thing (my payment's still pending, as I'm assuming everyone else's are). Apparently they've figured out the cause, but they don't have a specific timeline on when it'll be resolved. Good news that they're making progress on it though, at least.
This is the response I got from them this morning.......
Hello,
I'm **** from Amazon Payments team.
I'm sorry to know about the delay in the processing of your withdrawal that has been initiated on October 22, 2017.
I've checked with our concerned team and found that there is a known issue for withdrawals done on October 22nd, please be assured we have a team looking into it now and I have provided them with your account information.
Further, I'll personally follow up on this query and I'll get back to you as soon as we have an update.
Please be rest assured that we will take every action possible to prevent you from bearing any loss.
Thanks for your patience and understanding.
We'd appreciate your feedback. Please use the buttons below to vote about your experience today.
Best regards,
****
Amazon.com