CKinMD

I'm not entirely sure I am understanding the issue. Are you saying that your Mosaic status is not being recognized, or the JetBlue (it's B6, by the way) segment isn't being ticketed at all? It's the part where you mention getting it reinstated that is confusing to me.

Have you tried calling someone from the AMEX help desk and having them open a ticket to investigate? I would be pretty surprised if there is in fact a glitch in ticketing, and I suspect there is a relatively easy fix.

I assume booking two one ways is not an option for you, for some reason? Unless you're booking airlines within th same alliance, I don't see the benefit to you booking two separate carriers on the same reservation (unless of course you're trying to avoid a separate transaction fee....in my case we're charged north of $15 for every transaction, but they don't seem to care that I often book direct with the airline).

Are you adding any notes to your reservation specifically asking to have your Mosaic number added to "B7"? If so...that may be why your number isn't sticking....and you may be an elite with Uni Air out of Taiwan without even knowing it.