It's hard to monitor and manage hundreds of coins chains and daemons. Some of wallets will always fail, some chain hardforked and all these events have potential of losing clients money.
Also business processes on most of the exchanges are more like amateur than enterprise grade.
So it maybe wise to block a coin and then begin to find out what's happening. With such a policy and steem often hardforks it's not a surprise than it gets perma-blocked.