I'm not at all surprised that the recommended solution to this problem did not work. I submitted a Post about two weeks ago questioning how loosening the cocking levers might permit the forend to be released. For whatever reason, my Post did not appear.
The Deeley and Edge forend latch system isn't at all complicated, whether of the type where the notch on the barrel forend loop faces forward, or the slightly more complicated version where the notch on the barrel forend loop faces toward the rear. The problem was stated by the OP in his second sentence, "The lever only lifts partway and doesn’t disengage from the hook, even if I put quite a bit of pressure on it..."
I just didn't see how the cocking levers might interfere with the the forend release lever moving to the full unlatch position. It would be interesting to hear what the eventual solution is. Unless whatever is preventing the release lever from moving to full open position can somehow be dislodged, I'm guessing it will involve splitting or otherwise damaging the forend wood.
