I solved my problem.
In my case this has helped me https://www.prestashop.com/forums/topic/458057-error-using-1-click-upgrade/?p=2171426
-> Make a full backup first
-> Download the latest stable Prestashop version
-> Extract the folder
-> Open the folder and you will get 2 subfoders: Prestashop and Install_PrestaShop.html
-> Copy/Paste ONLY the Prestashop subfolder here: /admin/autoupgrade/latest/
-> Go to 1 Click Upgrade module -> On Start your Upgrade field click the button on the right named More options (Expert mode) -> Go to Expert mode -> Channel -> select Local directory -> write the presta version you are ungradeing to (ex: 1.6.1.1) -> Save -> On Backup Options field -> Back up my files and database -> select No -> Save -> On Upgrade Options fiend -> Disable non-native modules -> select No -> Save -> Check if above settings are made -> then Upgrade the version
It works for me