Thanks for the report!
That is very close to my experience and exactly why I burn-in my cables AND receptacles. The burn-in service for the GTX NCF receptacles is very valuable if you don't want to experience these "strange and wild swings in tonal balance".
And I provide burn-in, shipping and maybe even more (?
) for free...
For the best clarity and natural sound my PL 11 power cable with the NCF plugs is about as good as it gets. Furutech's DPS-4 is a great choice for those who want a little midrange bloom and slight warmth while still retaining great detail.
I also have a brand new UPOCC SILVER ribbon power cable that'll be ready to go very soon, about a week or two away.
This UPOCC silver PC is intended for source components, and paired with my PL for amps and power distributors will be the best solution for powering a system on the market today... imo.