I've only had it happen with friends, but it happens a rather decent amount of time, but only on the new client. All I know is that either myself or friends accept a match, have the accept circle sit there for an unusually long time then get told that that person failed to accept a match. It turns out that what's actually happening is that the match is being declined by somebody else, then another one pops, except not for the person with the previous accept match circle because their previous one is still up, thus denying them the option of the new match acceptance. This has probably happened about once or twice every 3-5 matches. I only play with friends, so I don't know if this is a friend only thing or not.