The bug

Respawn anchors do not produce ambient sound, although a sound file for it exists (sound id minecraft:block.respawn_anchor.ambient)

To reproduce

1. Place a respawn anchor.
2. Charge it with glowstone.
3. Wait.

Expected result

The respawn anchor would produce its ambient sound.

Observed result

The respawn anchor does not produce its ambient sound.

Code analysis

Code analysis by TkainMinecraft can be found in this comment.