Ric, Almost everyone loves their 1.4 x Nikon TC's, but if you look at B&H reviews you will find about 3 reviews out of about 160 that describe your results. More or less. Before blaming your TC however I would make sure of my results. How are you testing? How is your camera metering set up? What is the distance used? Mansurov has at least two useful articles and he describes the LensAlign sytem and FoCal. You can also visit the lensalign website for more info. My apologies if you are already aware of the preceeding!
I would think that if you do a good job of cataloging your shots with the issue then these shots could be emailed to Nikon tech for evaluation. I don't think that sending the TC to them with a complaint will accomplish much - you are likely to get the TC back with no changes - give them evidence though and it's another issue. Do you have a way of trying another 1.4 TC for comparison?
Also, and as an aside, I allowed a friend of mine the use of my 500mm while we were shooting raptors at a nearby marsh. He used the lens in combination with his D800 and a 2.0 E III TC (tripod mounted.) He backfocuses and on the 800 the AF-ON button initiates VR. That night he emailed me asking if I'd noticed any softness with this lens before. The short answer is that somehow the VR had been switched on, and that issue now is something else to check before a shoot. Good luck!
I am Using a chart I printed off "the net" (It has a focus point that is 45* from the chart that has .1cm increments) and setting the camera on a tripod. I am approximately 40' from the chart. I read that it is recommended to be 8 feet per 100mm of lens. ISO 100, Lens wide open, VR off, and using a remote shutter release once focus is achieved.
I do notice that things are sharper with VR off when using a tri-pod.
I don't have any access to another 1.4. I'm not exactly living "in town" and the town I live near ( 50 min. drive) isn't a huge metropolis.
I suppose I could go through all the trouble of proving things to Nikon.
Does anyone rent or lend out the Lens Align system?
Ric, I think that you'd be hard pressed to find someone who rents the LesAlign system. I also can't comment on your test at all - a small error can lead to relatively large focus adjustments, but soft is soft and we don't need test results for that. One option that I can think of for you is to rent another TC. Lensrental has them and although you can't do the test NOW their fee is only $25 and change for a four day rental - I'd guess that there is an additionl fee for shipping.... Their price for the 2x (or 1.7x)is pennies higher and since you had questions in another post about the 2x III you could kill two birds with one stone for slightly better than $50.00 or so. When you confirm that your 1.4 is maladjusted/defective you might ask Lensrenal about your course of action, since I am sure that they run into this situation from time to time. Also - you need to check on whether you have the USA model or graymarket. How old/new is the TC? Returning it to the vendor is yet another option.