QC can also be incomplete with Custom Shops.
My Schecter Nick Johnston Custom Shop USA came with the Tone Pot ungrounded. No problem while touching the strings or the volume pot, but it was noisy when lifting both hands from the strings, and a hell of a noise when touching the tone pot knob without touching the strings.
I had to solder a wire between the vol pot and the tone pot.
That was the first batch of the NJ model (they came with Seymour Duncan Antiquity Texas Hot, not with Schecter pickups). Perhaps the builder thought that the aluminum foil would do the job, but that is not the case.
View attachment 83007