My Unity standart cube mesh i changing when i hit play?

Hi, thanks for our time.
When i open my unity projekt everything look’s fine, but when i hit play, all of my objects that has a cube-mesh becomes flat.
When i stop play-mode the mesh stays like this.
Anyone tried this before?
Anyone knows how I can access this type of mesh?

Really hope that you can helt me out.
Cheers - Frederik

Well it’s pretty obvious that you have some code in your project that directly manipulates the default cube mesh object. Of course this change will persist like any change to assets. However the change will not be serialized since the built-in cube mesh is part of Unity. So when you restart Unity such changes would be reverted / reset.

You should generally avoid messing around with build in assets. If you have some code that should manipulate a cube mesh you should first duplicate the mesh (simply by using tmpMesh = Instantiate(originalMesh); ).