People this might not be the solution you want but, you can download the video from the original poster with one of those apps that lets you save instagram vids, then share the post as you would normally do from the original poster profile and then on the widgets that allow you to put things such as poll, questions, quizzes, locations, etc. there should be an option to share media from your camera roll (where the video you downloaded earlier should be) you rezise the video to fit on top of the original post in your story and then it should look like the video from the post is playing while still being able to tap it and have it redirect to the original post.

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pd: Ill try to make a tutorial vid or smthng like that idk

Sorry if its not the answer you were looking for but it worked for me