Signs, banners, end rods and anvils mirrored incorrectly

Standing signs and banners, end rods and anvils are incorrectly reflected with the reflection feature of "load" structure blocks.

Standing signs and banners have the wrong rotation value after being flipped.
I got these results when flipping along the X axis:
Original rotation, Flipped rotation, Expected rotation
0, 8, 0
1, 7, 15
2, 6, 14
3, 5, 13
4, 4, 12
5, 3, 11
6, 3, 10
7, 2, 9
8, 0, 8
9, 15, 7
10, 14, 6
11, 13, 5
12, 12, 4
13, 11, 3
14, 10, 2
15, 9, 1

End rods seem to be flipped along the wrong axis (X-Z). For example, an end rod flipped along the X axis acts as if it was flipped along the Z axis.

The rotation of anvils is not being changed at all. A similar block, the fence gate, is flipped correctly.