Dear Bart

Here is the script I am currently using. Please let me know what your thoughts are on this.
This script is able to create a group, but it comes empty without any child elements for some .ifc models, but for others, it actually comes with child elements while duplicating the elements and placing them randomly in space.

from typing import TYPE_CHECKING

from NemAll_Python_BaseElements import CommonProperties
from NemAll_Python_BasisElements import (ModelElement2D,
                                         ModelElement3D,
                                         ElementGroupProperties,
                                         ElementGroupElement)




from CreateElementResult import CreateElementResult
from ScriptObjectInteractors.SingleElementSelectInteractor import (
    SingleElementSelectInteractor, SingleElementSelectResult
)
from TypeCollections.ModelEleList import ModelEleList
from BaseScriptObject import BaseScriptObject, BaseScriptObjectData

if TYPE_CHECKING:
    from __BuildingElementStubFiles.InputInteractorBuildingElement import (
        InputInteractorBuildingElement as BuildingElement
    )
else:
    from BuildingElement import BuildingElement


def check_allplan_version(_build_ele: BuildingElement, _version: str) -> bool:
    return True  # support all versions


def create_script_object(
    build_ele: BuildingElement,
    script_object_data: BaseScriptObjectData
) -> BaseScriptObject:
    return GroupTwoElements(build_ele, script_object_data)


class GroupTwoElements(BaseScriptObject):
    def __init__(self, build_ele, data: BaseScriptObjectData):
        super().__init__(data)
        self.build_ele = build_ele
        self.sel1 = SingleElementSelectResult()
        self.sel2 = SingleElementSelectResult()
        self.step = 0

    def start_input(self):
        self.step = 1
        self.script_object_interactor = SingleElementSelectInteractor(
            self.sel1, prompt_msg="Select first element"
        )

    def start_next_input(self):
        if self.step == 1:
            self.step = 2
            self.script_object_interactor = SingleElementSelectInteractor(
                self.sel2, prompt_msg="Select second element"
            )
        else:
            self.script_object_interactor = None

    def execute(self) -> CreateElementResult:


        basis_elements = []
        for sel in (self.sel1, self.sel2):
            adapter = sel.sel_element

            # 1) Get the element's own properties & *local* geometry
            cp = adapter.GetCommonProperties()
            geom = adapter.GetGeometry()   
            # <<-- LOCAL geometry!

            # 2) Wrap in a true BasisElement
            if adapter.Is3DElement():
                elem = ModelElement3D(cp, geom)
            else:
                elem = ModelElement2D(cp, geom)

            basis_elements.append(elem)

        print("SELECTED ELEMENTS", basis_elements)

        # 3) Prepare group properties
        group_cp = CommonProperties()
        group_cp.GetGlobalProperties()        # <<-- place group in model
        group_props = ElementGroupProperties()
        group_props.Name           = "MyGroup"
        group_props.ModifiableFlag = True     # <<-- allow opening to show children
        # group_props.SubType     = <whatever subtype you need>

        # 4) Create the group in *local* coords
        group = ElementGroupElement(group_cp, group_props, basis_elements)

        # 5) Return it
        ml = ModelEleList()
        ml.append(group)
        return CreateElementResult(elements=ml)

Cheers.