Here is what the bug is causing to happen. If you are the original target of the shackle, you can still be broken out normally without any issues but what is happening incorrectly is that if any additional players are hit by the shackle, they cannot be broken out by another player. However, any form of CC break ability that player has will still work.
I'm not sure, but I think it's a litle bit different issue.
From my experience and this mention about primary/secondary targets, it seems like issue is schackless not appearing/working on secondary targets, and also being unbreakable by normal means. So only thing affecting secondary targets is fact that they can't break out others(but then they don't need breaking out themselves, because they are not affected by root).
There are 2 things I noticed in my attempts today that support this version. First, I'm almost certain we didn't get more than one snare in single hit at any time, and it was always melee that had trouble breaking out shackles on other melee. Secondly, as I've mentioned earlier, I couldn't break shackles on tank untill I got shackled myself, used root break and then ran to free him.
Sure, I could be wrong, but if not, it means workaround is a little bit different. - if you can't stay apart(3 melee), task person that can(healer) with always breaking out affected target.