iframe integration on a website page don't scroll to the top of the iframe when you click on a job at the end of the frame

The problem occurs when you are putting the iframe further down on a page like we did for our client:
https://www.dtad.com/de/karriere

If you don't click on one of the top positions then it starts displaying the job description in the middle of the personio single page. We know that you recommend to use a script in order to solve this, but when we insert it, it scroll to the top of the web page, and not to the top of the iframe.
window.scrollTo({top: 0, behavior: 'smooth'});

Any workaround in javascript so that it can scroll to the top of the iframe container only?
Thank you for your suggestions.
Note: We have the same issue for another client using personio too: https://www.fincite.de/en/career )