This is what I found in the console stacktrace when this happens:
main.js:2349 Uncaught DOMException: Failed to execute 'drawImage' on 'CanvasRenderingContext2D': The HTMLImageElement provided is in the 'broken' state.
at Object.draw (https://v6p9d9t4.ssl.hwcdn.net/html/4254368/castle-builders/main.js:2349:21)
at Object.drawBackground (https://v6p9d9t4.ssl.hwcdn.net/html/4254368/castle-builders/main.js:1544:25)
at Object.drawFirstPaint (https://v6p9d9t4.ssl.hwcdn.net/html/4254368/castle-builders/main.js:856:14)
at drawScreen (https://v6p9d9t4.ssl.hwcdn.net/html/4254368/castle-builders/main.js:2393:19)
at Object.core (https://v6p9d9t4.ssl.hwcdn.net/html/4254368/castle-builders/main.js:483:9)
at animate (https://v6p9d9t4.ssl.hwcdn.net/html/4254368/castle-builders/main.js:2429:25)