Dragon Invasion Thorndale siege issue
 

I sieged Thorndale 2 times and both times, just as I was about to win, the game freezed and I had to end its process. Is there any way to avoid this crash or is it common?

Thanks for reporting this, we are looking into it. We do know that some players were able to Liberate Thorndale just fine. I would recommend trying to start the siege from a different starting location - you know how you select your starting location after Thorndale cinematic - that might fix the issue.

The dragon king there is also inmune to arrows and bolts
 

I have beseiged the city as well, but I do manage to destroy the goblin army and the green and red dragons, but the king, because he is inmune to arrows and bolts.