I share the same issues as @baileyniemiller except I used “INSERT HEADERS AND FOOTERS BY WPBEGINNER” and “Ad Inserter – Ad Manager & AdSense Ads” and both showed a “Warning” followed by code on top of my header. Troubleshooted both and it all stemmed with Yoast. Even after deleting the header and footer plugins the code I entered in the header still showed which was odd(cleared cache even). But it did not disappear until I deactivated Yoast and reactivated it for it to finally disappear.
So it seems there a 3 header and footer plugins currently of recent that has errors with Yoast.
