Issues when using Mirror modifier

[Barbscoa]

Hi!

I’m using the mirror modifier on this piece, but when I try to modify a Vertex, it’s like Blender is creating new vertexes.

Any idea of why this happens? If I move it to both axis manually it only moves one vertex.

Thanks in advance!

[FedPete]

I think you have still a duplicated object!
The mirrored one and something else which has no middle edge to mirror against.

Use MAIN MENU > WINDOW > SAVE SCREEN SHOT.