If you follow POP's recommendations your page is unlikely to move down in Google search results, but it can happen.
Drops sometimes occur when something has been removed from a page. If your page has moved down, check that you didn't accidentally remove anything (anything at all) from your page.
What to do if your page has dropped
• First, give your changes enough time to work. If, after waiting for at least 10 days, your position is still lower, put any removed content back.
To be able to undo changes, it's essential to keep a record, for example by saving your page content in a note on your phone.
• If you only added content to your page, and didn't remove anything, and your position in Google has remained lower for 20 days, undo your last changes.
If you undo changes which had a negative impact on your position in Google, you will usually get your ranking back.