Brochure site fails repeatedly and randomly: "line 49 of core/modules/views/src/Element/View.php"

My site, which is essentially “read only,” randomly fails to load, with the following message: The website encountered an unexpected error. Please try again later. Error: Unsupported operand types in DrupalviewsElementView::preRenderViewElement() (line 49 of core/modules/views/src/Element/View.php). Here are the environment specifics:    Hosting environment: Pantheon (Personal[…]