When I choose Appearance -> Customize, all I get is an error message:

Call to undefined method ElementorUtils::is_ajax()

There's also some other new problems, don't know if they're related:

The Vimeo video on the front page only shows up if you are logged in
The NextGen Gallery on the front page doesn't work right if Ajax pagination is turned on (it doesn't show latest images right away).

Thanks,

Manu

Thank you. 

The video problem got fixed, but the Next Gen Gallery still isn't showing the latest images, unless I first click on some other image page in the pagination and then go back to first page... 

Actually the Gallery started working after deactivating and reactivating it. 

So, thank you again for a good support!

Manu