If you place multiple Nixie Tubes next to each other you can look into the ground if you look through one tube onto the other. This seems to have some rules:

1. You can only see into the ground if you look into the direction you placed the tubes after another
2. On some blocks the Tubes seem to be "imune" to the effect
   Heres a video of me researching the bug: https://youtu.be/RYq0FxguJw0

Are you using optifine? Or fabulous graphics? Also make sure that you are on the latest version of Create.

Im not using optifine, my graphics is on fast and I have the latest version, maybe my Computer is too bad, maybe others have the same problem...

do you have any other graphics/performance enchancing mods?

yes, a mod called chlorine, I think it´s in beta so it could cause grafical issues

Remove that and see if the issue still occurs.

does not occur, guess that means isn't creates fault