This is the same issue described in MC-199238.

The bug

Inside of dragon eggs, multiple faces exist that cannot normally be seen without clipping inside of the egg block.

How to reproduce

1. Place a dragon egg
2. Enter Spectator mode
3. Fly inside the dragon egg

Expected results

The upper faces of the cuboids below the widest ones and the lower faces of the cuboids above the widest one, would not exist.

Actual results

They do.

How to fix

Get rid of these faces. The resource pack attached to MC-199238 will probably help and can be use as a guide.