Hi Coffinmaker,
I think I found the problem. If you remove the forend, there is a steel coverplate, screwed into the forearm wood. Remove that, and you have the latch assembly and a loose piece of steel that will fall free when the coverplate is removed: the aforementioned "forend lever bolt", which actually is the forend's engagement surface for the barrel lug, cammed into place by the latch itself.
After flipping that forend lever bolt piece over and reassembling with some light tapping, the forend snugged up against the barrel much tighter than it did when I first bought the shotgun (not long ago).
When time permits, I'll try to get a photo of this. This piece can easily be installed upside down, so a photo of it might be good for reference for anyone who takes their forend down for refinishing.
Thanks for your assistance.