I don't understand why Panasonic introduced a "HDMI YCbCr Range" parameter.
Actually only RGB is meant to be used with full range (0-255). It is mostly used by PC and consoles.
YCbCr should be always limited range (16-235), that's how content is encoded on blu-ray discs, including Ultra HD discs.
You should leave this setting on "normal". The black crush is either how the content really is or your other picture settings being wrong.
You should read that:
HDMI Enhanced Black Levels, xvYCC and RGB
edit: after a deeper search, I'm partly wrong, there are actually some UHD blu-ray discs encoded in 0-255 instead of the usual 16-235.
According to this source:
[Test 4K Ultra HD] Divergente , this is the case at least for:
- Divergent
- The Expendables 3
- Ender's Game