extend worker sent an error! Uncaught TypeError: Cannot read properties of undefined (reading 'Callback')

[Alexufo]

v 3.1.60,v3.1.64

I use this simple example in my project and it works for non pthread building.
https://emscripten.org/docs/porting/connecting_cpp_and_javascript/embind.html#extend-example

But then I compile with pthread I got random (through one or two page reloads) error:

worker sent an error! https://localhost:4443/wasm.js:71: Uncaught TypeError: Cannot read properties of undefined (reading 'Callback')

      const delegate = MODULE.Delegate.extend( "Delegate", {
        __construct: function () {
          this.__parent.__construct.call(this);
        },
        __destruct: function () {
          this.__parent.__destruct.call(this);
        },
        Callback: function (jmessage) {
          console.log(jmessage);
        },
      }
    );
    
    let d = new delegate();

How can I try to figure out what the cause of the error is?