Okay so I tested it and the error sees to happen on my google chrome browser where this error will appear. However, if I use any other browser instead, the error never pops up. Here's the error. I found a work around by just using Opera instead but it's just an odd thing I discovered.
That… is weird. 😅 Thank you for sharing the screenshot!
A few readers mentioned getting that error between updates, like when they tried playing an old save after an update. Best guess is that there’s something going on in the cache. I would recommend clearing your browser cache and starting over. Unfortunately, it means starting from the beginning, I’m sorry.