As far as I can tell, it's not universal, but still somewhat common. (My computer has always done it ever since I bought it new in April.) It is a bit annoying. But since I use the MAS so irregularly, I can get by. I do wonder what the cause is, though. I'm less certain I'd like to know how Apple have so far failed to get to the bottom of it.

On OS X and iOS Apple’s developers tend to treat every network error as a reason to nag you to reauthenticate. I have opened bugs for this in almost every app they make and it's like playing whack-a-mole where they'll fix one instance in one app and then it'll show up in the major release or a similar function somewhere else.

Do you know for certain that they know about it? You can file bugs here: http://bugreport.apple.com/.

Radar is bullshit. Apple should make it easy to file bugs and get information about them but they've been using this piece of jank since forever. If I file a dupe I have to inquire about it every now and again because you can't just add me to the original? Yeah, I don't think so.

I've done my Radar time.

If the reason Apple haven't fixed this is that I personally didn't sign on to Radar and log it as a bug, I can live with that.

I've had the same issue. And yes, it's annoying. The MAS is frustrating at the best of times.