Hi!
When i try download map first time after launch game, i god freeze game for 60-90 second, some time crash and always disconnected from BattleNET. After second launch, the game work more stable, but freeze 30 sec too on downloading map.
Didn’t you think your devices might be the problem? Test your devices and connection( speed, packed losses - tracert, etc.). Search for the addresses of the game’s servers on the network and do tracert.