I just finished up my first Magic Mirror build. I updated Magic Mirror today as well as other modules it told me where out of date. After updating I started adding re-occurring tasks to my Google Calendar. I realised that these tasks are doubling. They display on the day the are supposed to occur as well as the day after. This does not occur for re-occurring tasks I added before updating.
Its a pretty Vanilla install I am using the Calendar EXT3 module for my Calendar. I’m not really code literate, just good at following directions

My Config File

						// - another specific IPv4/6 to listen on a specific interface
							// - "0.0.0.0", "::" to listen on any interface
							// Default, when address config is left out or empty, is "localhost"
	port: 8080,
	basePath: "/",	// The URL path where MagicMirror² is hosted. If you are using a Reverse proxy
									// you must set the sub path here. basePath must end with a /
	//ipWhitelist: ["127.0.0.1", "::ffff:127.0.0.1", "::1"],	// Set [] to allow all IP addresses
	ipWhitelist: [],
									// or add a specific IPv4 of 192.168.1.5 :
									// ["127.0.0.1", "::ffff:127.0.0.1", "::1", "::ffff:192.168.1.5"],
									// or IPv4 range of 192.168.3.0 --> 192.168.3.15 use CIDR format :
									// ["127.0.0.1", "::ffff:127.0.0.1", "::1", "::ffff:192.168.3.0/28"],

	useHttps: false,			// Support HTTPS or not, default "false" will use HTTP
	httpsPrivateKey: "",	// HTTPS private key path, only require when useHttps is true
	httpsCertificate: "",	// HTTPS Certificate path, only require when useHttps is true

	language: "en",
	locale: "en-US",
	logLevel: ["INFO", "LOG", "WARN", "ERROR"], // Add "DEBUG" for even more logging
	timeFormat: 12,
	units: "imperial",

	modules: [
		{
			module: "alert",
		},
	
		{
			module: "updatenotification",
			position: "top_bar"
		},
		{
			module: "clock",
			position: "top_right"
		},
		{
			module: "calendar",
			position: "top_right",
			config: {
				//wrapEvents: true,
				broadcastPastEvents: true, // <= IMPORTANT to see past events
				calendars: [
					{
			fetchInterval: 300000,
			url: "https://calendar.google.com/calendar/***/basic.ics",
                        name: "Shandra", // <= RECOMMENDED to assign name
                        color: "blue" // <= RECOMMENDED to assign color		
					},
					{
					url: "https://calendar.google.com/calendar/ical/en.usa%23holiday%40group.v.calendar.google.com/public/basic.ics",
                        name: "us_holiday", // <= RECOMMENDED to assign name
                        color: "red" // <= RECOMMENDED to assign color
					},
				]
			}
		},
		{
            module: "MMM-CalendarExt3",
            position: "top_left",
            title: "",
            config: {
                    mode: "month",
                    instanceId: "basicCalendar",
                    locale: 'en-US',
                    maxEventLines: 6,
                    firstDayOfWeek: 0,
                    calendarSet: ['us_holiday', 'abfall', 'mytest', 'Shandra'],
        }
	}, 
		{
			module: "compliments",
			position: "bottom_center"
		},
		{
			module: "weather",
			position: "top_right",
			config: {
				weatherProvider: "openmeteo",
				type: "current",
				lat: 44.9429,
				lon: -123.0351
			}
		},
		{
			module: "weather",
			position: "top_right",
			header: "Weather Forecast",
			config: {
				weatherProvider: "openmeteo",
				type: "forecast",
				lat: 44.9429,
				lon: -123.0351
			}
		},
		{
	module: "MMM-Traffic",
	position: "bottom_right",
	config: {
		accessToken: "pk.eyJ1IjoibW1ydXN0eWtheW42NiIsImEiOiJjbTE0MjFweGYxa3BwMmxvcnJqb2kzZTQ5In0.1_",
		originCoords: "-",
		destinationCoords: "-",
		showSymbol: false,
		firstLine: "{duration} mins",
		secondLine: "Home to Schirle Elementary"
	}
    },
    		{
	module: "MMM-Traffic",
	position: "bottom_right",
	config: {
		accessToken: "pk.eyJ1IjoibW1ydXN0eWtheW42NiIsImEiOiJjbTE0MjFweGYxa3BwMmxvcnJqb2kzZTQ5In0.1_HtZ4tllgp8MkK41SkAAQ",
		originCoords: "-",
		destinationCoords: " -



",
		showSymbol: false,
		firstLine: "{duration} mins",
		secondLine: "Home to Work"
	}
    },
    {
    module: 'MMM-Remote-Control',
    // uncomment the following line to show the URL of the remote control on the mirror
    position: 'bottom_left',
    // you can hide this module afterwards from the remote control itself
    config: {
        customCommand: {},  // Optional, See "Using Custom Commands" below
        showModuleApiMenu: true, // Optional, Enable the Module Controls menu
        secureEndpoints: true, // Optional, See API/README.md
        // uncomment any of the lines below if you're gonna use it
        // customMenu: "custom_menu.json", // Optional, See "Custom Menu Items" below
        // apiKey: "", // Optional, See API/README.md for details
        // classes: {} // Optional, See "Custom Classes" below
    }
},
		/*
	    {
			module: "newsfeed",
			position: "bottom_center",
			config: {
				feeds: [
					{
						title: "New York Times",
						url: "https://rss.nytimes.com/services/xml/rss/nyt/HomePage.xml"
					}
				],
				showSourceTitle: true,
				showPublishDate: true,
				broadcastNewsFeeds: true,
				broadcastNewsUpdates: true
			}
		},*/
	]
};

/*************** DO NOT EDIT THE LINE BELOW ***************/
if (typeof module !== "undefined") { module.exports = config; }