I hope you are well today and thank you for your question.
It seems this is happening because of the Jetpack plugin Photon module that you are using on your site so could you please try temporary deactivating it or its Photon module on your site?
This jetpack photon module is not updating the images stored on wp.com so to resolve the issue either disable this module or update the images on wp.com by contacting jetpack support team.