Alpha overlay issues

I got several objects mapped with a transparent png as diffuse map.
Problem is that when 2 or more objects overlap each other, the overlapping areas are no longer transparent.

I thought that depthWrite and depthTest should over come that issue, but maybe I’m missing something.

The material is created during runtime:

object.material = new v3d.MeshBasicMaterial({
                    map: imageBitmap,
                    transparent: true,
                    depthWrite: true,
                    depthTest: true
                });