When AWS initially started offering domain registrations, I transferred a few domains (that I'd already been using Route 53 for) over to keep everything in one place.

A few months later, I wanted to transfer them elsewhere, but quickly realized that the auth codes in the AWS interface had expired, with no way to renew them. I didn't have a support subscription since I only used the AWS account for these 4 domains + Route 53 and I wasn't about to pay Amazon 30$/month to get them to fix their own mistakes.

I naïvely tried contacting billing support (the only one you can contact for free, go figure) in the hope they could forward the bug report, but while they were very apologetic, there was nothing they could do.

So Amazon took my domains hostage for 6 months until they eventually figured out the bug on their own. Have not touched anything related to AWS ever since.