This happens to me from time to time and normally fixes itself. It's been happening more frequently so I wanted to see if maybe someone else was having the same problem or knew what I could do to track down the cause.

Basically, I will pop out a Mini List for a quest chain and half (or most) of the quest names will be numbers instead of the names. I've attached a screen shot to show what I see. I've searched to see if anyone else has had this issue recently and I don't see anyone else listing it but I figured it was worth a shot to ask.

I love this addon and any help is greatly appreciated. Thanks so much in advance.

As far as I know, it's just Blizzard being Blizzard, not on our side but theirs. Sometimes they return quest data unreliably/too slow and as you said it just resolves itself.

This sort of thing will always happen on reset day, especially for old quests and is not in our control due to how servers cache quest information. If a given Item/Quest has not been loaded/seen/picked up by any player yet since the server reset, it will not return information when requested by an API call.
Otherwise, we rarely have any 'hard-coded' Quest names in the addon, and it is explicitly for quests which do not return a name from the in-game functionality.