making a ground out of cubes

dear community, i kind of got a weird problem, i stacked some cubes next to each other so they build a ground, yes the ground needs to be made up out of several cubes cause i want the individual one to change colour later. But if i move the player now it drops in between these cubes and goes into a kind of diagonal position. how does this come?

thanks for help

 

Are cubes static? Do they have matching colliders?

 

they are both box and mesh colliders, thats what you ment with matchingcolliders coorect? both rigidbody as well

 

hmm if i just duplicate the cube it works