short answer: its a feature
confusing long answer: that isn't a bug btw its suppose to work that way. while its vetoed if it doesn't find a game in an aloted amount of time or there are no games it will add the veto maps back in the pool. to increase game finding speed. basically it cna't find a game at your level fast enough so it looks in your veto list to.
Relic said that vetoes only come in effect after you get a match. That way you dont miss out on any matchup