When placing an arrow into an item frame, the orientation of the arrow appears to be mirrored in the vertical axis when using Chroma Hills compared to the default resource pack.

Example:

• Using the default resource pack
  • An arrow placed in a newly placed item frame will have the tip pointing to the top right corner
• Using Chroma Hills
  • An arrow placed in a newly placed item frame will have the tip pointing to the top left corner

This can also be seen by building a few 3x3 squares and placing an item frame in the middle containing an arrow set to any rotation.

OOO
O>O
OOO

Substitute the block the arrow is pointing to with any visually distinct block.

OOO
O>X
OOO

Quit, then add CH resource pack and reload the world.

The arrow will no longer be pointing at the unique block.

OOO
O<X
OOO

In my world I have a potion factory that uses the rotation of an arrow in an item frame to point to signs describing what sort of potion will be made when the "magic" button is pressed.

This bug means that the potion produced is not the potion that the arrow points to.

I've taken the machine apart and checked that the comparator is detecting the correct amount of power for the correct number of rotations of a newly placed arrow (it is).
This is purely a visual bug.