Also, people are usually like LOL it's just mRNA it goes away

But evidence does show it CAN go back to DNA with mechanisms familiar to anyone edgycated in molecular genetics - https://pubmed.ncbi.nlm.nih.gov/35723296/

Now, that particular study is in whatever cell line, highly dubious how it pertains to a human body, a few steps removed. But if you say "will you see this if you vaccinate 500 million times in 500 million people each with 500 trillion cells" - yea probably you would