Bucks 4X4 Center in Boise did my E locker a couple years ago. I was at the owners house for a BBQ last night so I decided to ask him why I have not experienced the "failing to unlock" others have.
He said you can not just throw one in and expect it to work well. You have to "massage" it. WTH is that??? Same thing as pulling a new revolver out of the box. Live with a rough 12# trigger pull or polish the guts for a smooth crisp 3 1/2# pull.
OTOH he said the ARB is a stronger locker with a more positive lock/unlock.