Hi Chuck! Your holiday season is going just great I see!
But seriously, if you replaced the Kroll with a known functional one and it still does not work in the VIP yet the Twisty does(???), then you do indeed have a contact/resistance issue in the King's Crown tailpiece somewhere. I would invest in some Caig's ProGold (must be
L100, no lesser numbers!) and follow the directions. It is basically a contact cleaner that you apply (comes in various formats such as needle dropper, brush-in-bottle, felt tip pen, etc.) on the affected surface/s (I would hit ALL the contact points/joints of the light since you'll be into it anyway) and then wipe off. You will usually get a nice black grunge after which you repeat until the cloth or whatever you use comes off clean, then a Very Sparing final application before screwing the parts back together.
If it STILL does not work then just send it back for a free service. All MR Bulk lights are Bulk-backed to the original purchasers (for a reasonable period of time, of course) - then again maybe I'm just in a holiday mood and will forget all about this come the new year (quick, send it now!)...seriously though, the Caig's will work wonders. Also very useful for stereo equipment contacts, VCRs, etc. And in even some of the really grunged-over poorly performing incandescents, cleaning the contacts makes them absolutely blast out the photons, visibly to the eye which means they become at least twice as bright. A good investment for all things electrical and not just the VIP.
Their webstore is
HERE.
Let me know how you make out.