Question about tumbler on Parker VH forend

[OldenHoo]

I am having issues with the forend on my gun. With some effort, I can get the forend to stay on. To test whether or not the forend is secure, I give a gentle tug on the end to see if it is seated properly and locked. Yesterday while I was shooting sporting clays, the forend fell of twice. Both times, the forend was secure before shooting.

Is the tumbler on the inside of the forend supposed to be spring loaded or free spinning as it is now? It will only spin freely when I pull the latch down otherwise I cannot spin the tumbler.

There is no marring on either the lug from the barrel nor from the wood or latch itself. Things seem to be seated correctly but maybe I'm missing something. On my Brownings, the forend will click but I realize that this locking mechanism is different. How else would I know it's secure?

Thanks in advance.