Moving objects upwards in unity's editor-window, moves the same object automatically further on z-axis

Hi,

I think the topic explains itself.

I'm creating a 2D JnR. Main Camera is Orthographic.

The Collision works just fine so far as long as the z-position of my blocks (on which the player can stand) is between ~ -0.5 and 0.5. I put all blocks in a folder in the scene-hierarchy. The first (or origin) block was created with z position 0. All dublicated blocks on screen have the same properties, until I move them upwards (or downwards). Moving upwards increases the z position. And vice versa. Not proportional, only a little bit. But when a block reaches a certain height, z-position is 0.5. With these blocks, the player won't collide.

I could fix this by either putting a script on the specific blocks that lock the z position to 0 or adding some code to the collision query (like -> collide also when transform.position.z+1f) or something.

Both solutions would work. I tested them. But I guess both implementations are dirty work. I'd rather know the reason of this strange behavior and fix it, so that I can place the graphics wherever I like (with z = 0, always). Any ideas?

Thanks in advance!

EDIT:

Well, unfortunately, I can't provide any screenshot or video (confidentiality issues) of the current project. I'm trying to find a way to show it with another project/graphics later (or tomorrow). But I don't really think that it's necessary. At least in order to understand what i'm doing.

short summary: moving Graphics/GameObjects (with the mouse) in scene-view (in order to place them to a position I want them to have)

unwanted side effect: z position changes.

By moving them upwards (or increasing Y) z slightly increases, too.

What I forgot to mention is that the z-value jumps back after I try to manually enter "0" in Inscpector->Transform Position->Z and apply it.

But the spinners are set to Y and X only. Moving the object upwards only by the y-arrow doesn't work either.

I believed it has something to do with wrong settings or so (which I could post here of course. Any suggestions?).