Forge Version: 37.0.109
Geckolib Version: 1.17.1:3.0.11
How to reproduce:

1. Commonly register 2 animated blocks with respective blockentities;
2. Join the game and place one animated block;
3. Place another animated block right on that block;
4. Quit & re-join the world;
5. The animated block below won't render ( like an invisible block but it's still interactable ) ( and then when its tiledata changed it re-appeared ).

Also tried to reproduce with the two blocks that Geckolib provided( Botarium & fertilizer ). However, they rendered as expected normally. But when my custom animated block was placed, one of those placed Geckolib-built-in blocks will also "disappear" after re-joining.

Self fixed, something wrong in the blockentities' NBT load & save codes