Cubik Studio

Is there a way to fix it?

Yes, blocks have culling to stop the game running slowly (less faces to render, more FPS).

You'll need to use a different block that supports transparency such as glass, etc. or modify your model so it doesn't reveal the edges of other solid blocks.

I have the same issue the block is inside the original boundaries but the parts of the model show the cave systems under the grounds, I can't find a fix anywhere to fix this issue, I would understand if it was through the block that it would cause problems but it am not I missing something here @HanFox
I used acacia_log, but have made the edges round to make it look more real.

Why would Mojang offer people the be able to change the blocks but not fully support custom models, it makes no sense.