@gabrieljenik
I do a quick fix for 5.X : https://github.com/SondagesPro/LimeSurvey-SondagesPro/commit/238735c6066d279da89d5710410526a763823c8a

But i think it must be in https://github.com/LimeSurvey/LimeSurvey/blob/master/application/models/services/CopyQuestion.php

So before inserting the new question we may need to update the positions of certain questions.
So dilema is where should that be done...?

I don't incline to do it in the CopyQuestion service, as to try to keep the service objective clear and narrow.
Maybe create a new service (could be reusable on other scnearios as importing questions or creating new questions or RC?

In fact, if talking about updating the service, I think there are things that would be good to correct in the service. For example, it would be good if instead of making queries like \Question::model()->findAllByAttributes(['parent_qid' => $parentId]); you could use the relationships of $this->copyQuestionValues->getQuestiontoCopy(). This way it is limited to what you are passing as parameters.

I don't incline to do it in the CopyQuestion service, as to try to keep the service objective clear and narrow.

Order are related to CopyQuestion (and Create question too, see related : 19900: Unable to set position (in group) of new question).

If you think we can keep it in Question::increaseAllOrderNumbersForGroup : i can apply same fix for master.

PS : i think we don't need a CopyQuestion service, or better : we need a lighter CopyQuestion using a NewQuestion service