"invisible edges" on racing ground after seperating ground into several tiles

Hello everyone,

I am working on a classic tutorial game, where a block slides over a ground with the aim to avoid obstacles.
First, I used one ground tile with a very large z-axis, which however caused problems with the fog working on android. As a solution for this problem I found the advice to use several smaller ground pieces, which indeed solved the fog problem.


However, creating lot’s of smaller ground pieces causes a strange new problem. There seem to be invisible edges now between these ground blocks, which cause my “block car” sometimes but not always (!?) to jump when passing over to another ground piece.


This is what the general scene looks like:

Obviously, I only changes one axis of each ground tile, expecting that this should lead to no “invisible” edges or something similar.

193061-ground-problems.png

Does anyone have an idea what could cause this problem?

The only idea I have is that something my cause either the “car block” or the ground blocks to slightly change there Y position. But I have not idea what or why this should happen?!

I would be very glad to get any advice!