For my resource pack, Lithos, I created animated textures for all sides of the Respawn anchor.  The result is quite strange.

The bottom of the block animates as expected, at the proper speed.

The sides of the block do not animate at all, however when feeding it glowstone, the animation immediately advances.

The top is the weirdest, it animates as expected when empty of charges, but at an irregular jerking speed when partially or fully charged.

 

In my case all sides have the same number of frames, and are set to the same frame sequence and timing in flip book_texture.json.

Attached is the relevant portion of that file:

{{

{\{ "flipbook_texture": "textures/blocks/respawn_anchor_side0", "atlas_tile": "respawn_anchor_side0", "ticks_per_frame": 50, "frames": [ 0, 1, 0, 2, 0, 3, 0, 1, 2, 1, 3, 1, 0, 2, 1, 2, 3, 2, 0, 3, 1, 3 ] }

, { "flipbook_texture": "textures/blocks/respawn_anchor_side1", "atlas_tile": "respawn_anchor_side1", "ticks_per_frame": 50, "frames": [ 0, 1, 0, 2, 0, 3, 0, 1, 2, 1, 3, 1, 0, 2, 1, 2, 3, 2, 0, 3, 1, 3 ] }, { "flipbook_texture": "textures/blocks/respawn_anchor_side2", "atlas_tile": "respawn_anchor_side2", "ticks_per_frame": 50, "frames": [ 0, 1, 0, 2, 0, 3, 0, 1, 2, 1, 3, 1, 0, 2, 1, 2, 3, 2, 0, 3, 1, 3 ] }, { "flipbook_texture": "textures/blocks/respawn_anchor_side3", "atlas_tile": "respawn_anchor_side3", "ticks_per_frame": 50, "frames": [ 0, 1, 0, 2, 0, 3, 0, 1, 2, 1, 3, 1, 0, 2, 1, 2, 3, 2, 0, 3, 1, 3 ] }, { "flipbook_texture": "textures/blocks/respawn_anchor_side4", "atlas_tile": "respawn_anchor_side4", "ticks_per_frame": 50, "frames": [ 0, 1, 0, 2, 0, 3, 0, 1, 2, 1, 3, 1, 0, 2, 1, 2, 3, 2, 0, 3, 1, 3 ] }, { "flipbook_texture": "textures/blocks/respawn_anchor_top_off", "atlas_tile": "respawn_anchor_top_off", "ticks_per_frame": 50, "frames": [ 0, 1, 0, 2, 0, 3, 0, 1, 2, 1, 3, 1, 0, 2, 1, 2, 3, 2, 0, 3, 1, 3 ] }, { "flipbook_texture": "textures/blocks/respawn_anchor_top", "atlas_tile": "respawn_anchor_top", "ticks_per_frame": 50, "frames": [ 0, 1, 0, 2, 0, 3, 0, 1, 2, 1, 3, 1, 0, 2, 1, 2, 3, 2, 0, 3, 1, 3 ] }, { "flipbook_texture": "textures/blocks/crying_obsidian_top", "atlas_tile": "crying_obsidian_top", "ticks_per_frame": 50, "frames": [ 0, 1, 0, 2, 0, 3, 0, 1, 2, 1, 3, 1, 0, 2, 1, 2, 3, 2, 0, 3, 1, 3 ] },}}