Maybe this topic is already outdated but still...
If I were you, I'd focus on the invisible dead horses that are seen on the screenshots. Unless ofc that's perfectly normal on your shard.
Older clients (2.0+, dunno when it was fixed) can easily be crashed by certain hues of items or speech, etc.
When you're saying they "track relogging clients" so that they can't login again, it would suggest it's in fact no tracking, but simply the items still lying there.