Glad resolved..

Sounded unpleasantly like scene corruption due FBX imports 'breaking bad'. You can see entire scene, but only parts will render. Poser has lost track of much, and saving scene as PZ3 is too late. What's lost is lost. You must close Poser, swear eloquently, have a mug of 'caffeinated' and start over...

Upside, if you parent an FBX's many (>>10) 'junior' sub-rigs to the 'master' sub-rig promptly after import, seems to avert such horrors. Hierarchy 'root' does not appreciate congestion by a surfeit of sub-rigs. Analogy is not overloading root folder of eg C: drive with a zillion individual files: organised into sub-folders, they're okay...