If you go to the authors page and follow the links to the authors websites, you will find some still in operation and others that no longer exist. I also searched and found a few other authors who got their rights back, other than Nathan and AC...
By the sound of it, this author has had his Ridan books delayed repeatedly and now they've been published, they're full of errors. He must be feeling bad enough already: telling him all about them seems a bit like kicking him while he's down.
And what will that achieve? The author can't do anything about it; only the publisher could correct those mistakes.