The soul lantern has a relevant 3 frame texture (like the normal lantern), but its animation definition is missing from the flipbook_textures.json file, so isn't being animated.

To verify:

1. Download and extract the template resource pack: https://aka.ms/resourcepacktemplate
2. Open textures/flipbook_textures.json in notepad
3. Search for "lantern"
4. Note the lack of a "soul_lantern" definition