So I manually downloaded the current build versions of V4.2 and M++ from DAZ and decided NOT to let DAZ do the installation this time. The only problems I've been having relate to the Head folder, so I decided to delete everything that was currently in there and replace it with the combined files from the latest V4.2 and M++ head folders -- a total of NINE files again. The same-named NINE files that previously wouldn't work correctly. Re-initialized and launched Poser; loaded V4.2 followed by M++. Now BOTH the eyes open-close function AND the head size morphs WORK correctly!!! Simply AMAZING!!! I've been trying to solve this issue off and on since I first bought Poser and the V4 models in Nov. 2017!!!

I can't see any difference in the contents of the latest V4/M++ Runtimes VS the one I got in Nov. 2017. I really think something in the DIM is corrupting some files when it does the installation. What does DAZ care about the performance of an old model of theirs still being used today by their main competitor -- and V4/M4 still quite popular with plenty of merchant support? Why would DAZ want to fix this problem? Exactly...

Thanks again to everyone who offered help to me in solving this frustrating problem It has been quite a learning experience for me. I hope this thread might help anyone else who encounters this anomaly in the future.