The binding problem was fixed in 1997 or so.
The problem is, many OLDER or slower-moving books had 15 years of stock already in existence. Because the presses would otherwise be idle, for economy of scale, etc. books were printed in HUGE runs.
A good chunk of the books have not only been re-printed with the new (fixed) binding technique, but they often have new, updated covers as well!
They were doing several things wrong with the binding. They had the wrong glue and/or temperature, they weren't "roughing up the binding" before applying the glue, etc. I've seen their binding process -- trust me, it works great now! :)
Matthew