Extra and in search form

sounds like the famous/infamous wpautop problem

some links – you can probably google and find others.
You can either remove the filter or assign it to a low/later priority so that it runs AFTER do_shortcode

https://www.simonbattersby.com/blog/2011/02/wordpress-wrapping-shortcodes-with-p-tags/
https://customcreative.co.uk/resolving-wpautop-and-shortcodes/