Product review (5 stars): Metal Inserts are not the problem.
Washing machine back in service. This has metal inserts. I used a socket of the same diameter as the metal insert and a beat-up extension to gently tap into place. Just a guess, but I believe the reviewers that have a problem with insert separation might be hammering the plastic/nylon coupler instead of just the metal insert which probably would lead to premature insert separation from the couplers.