I will note for the forum here on FT that last year around this time the same situation appeared to have occurred. Credits for the UA TB were taking longer than usual and people reported this notion of it being "patched" by AMEX. It turned out that the code they use was just backed up and being updated. Credits posted a few weeks later. While longer than normal we have seen this situation year after year.
I was wondering when someone would bring this up. I'm not 100% convinced the sky is falling just yet.