Just compared your review comments on squelch to the way my D808 behaves and have a couple of comments:
You observed that “While still pressing in the Tuning knob you can adjust the Squelch level by turning the Tuning knob clockwise to raise the squelch level from 1 to 9.”
On my example you do not need to hold the Tuning knob pressed in to adjust the squelch level (although it still works if you do hold the knob in while adjusting).
You observed that “In the Squelch mode you can also toggle the Squelch speed by short pressing the Tuning knob to switch between “Off, Fast and Slow””.
On my example a short press in of the tuning knob toggles between Off, Fast and Slow tuning (not squelch), e.g. on SW Fast = 5KHz steps, Slow = 1KHz steps, Off = 0KHz steps (i.e. tuning knob inoperative). This is as described in the manual and works the same regardless of squelch setting.
BTW, impressed that you've disassembled and inspected 12 samples of this radio - that's probably more than the manufacturer :)