Custom blocks render at a much smaller scale than Vanilla blocks inside sulfur cubes.
Demonstration
The attached screenshots demonstrate this issue. Custom blocks are represented via purple and white concrete. Spectator should be entered to observe the custom blocks being rendered inside them. The cyan concrete scaled correctly is a Vanilla block.
Reproduction
This issue applies to all custom blocks models, even built-in models.
These demo screenshots and code are taken from the behavior pack in the attached world for convenience. This world can be opened (in Minecraft Preview) for inspection or unzipped to access the code associated with such. If testing independently, ensure the “Drop 2 of 2026” experiment is enabled.
Thank you for helping us improve Minecraft! We saved your files: