Had the same problem on my old D2a, very common and very frustrating. Tip. Never fit a cargo barrier that cannot be removed from the rear seat side. I found the push/pull/swear method worked most of the time otherwise a short trip along a suitably bumpy track did the trick. Eventually I dismantled the whole mechanism and gave it a thorough clean with Brakekleen (or other non oily cleaner) and thoroughly lubed it with powdered graphite which solved the problem till we retired the Disco from outback travel.
Deano :)

