Object not working?

Question

Vue.js

I do not know how to describe this question correctly knowledge is not enough.

There is a 'vued3tree' component in general, such an object gets into it

tree1: {
        name: "father",
        children: [
          {
            name: "son1",
            children: [{ name: "grandson" }, { name: "grandson2" }],
          },
          {
            name: "son2",
            children: [{ name: "grandson3" }, { name: "grandson4" }],
          },
        ],
      }

And everything outputs well, but if, for example, I drop it like this
this.test = this.tree1
and naturally write :data="test" in the component's data,

then this error

[Vue warn]: Error in nextTick: "TypeError: Cannot read properties of undefined (reading 'x') "
app.js:70726 TypeError: Cannot read properties of undefined (reading 'x')

What could be the problem? I also can not get from the database and after the object converted to js.