In 24w33a the UV for all arrows (and bee stinger) were split into two textures. However, the Programmer Art spectral arrow wasn't changed so now its invisible from some angles.

Steps to reproduce:

1. Enable the Programmer Art resource pack
2. Shoot a spectral arrow at a block from above
3. Move downwards and look at the spectral arrow

Observed result:
The spectral arrow is almost invisible at certain angles.

Expected result:
The spectral arrow is visible from all angles, like in 1.21.1: