We use several libraries and use a utility called Composer to manage the dependencies between them. We try and keep our Composer library up to date but not all plugins do and sometimes we find conflicts with other plugins. Try disabling your other plugins until the error goes away and then contact that plugin developer to update their Composer files.
I’m getting an error in my PHP log like: Fatal error: Call to undefined method Composer\Autoload\ClassLoader::set()
