It's a lot to ask for so no pressure, but since it's running on a webpage it would show up in the developer console in your web browser. For example, in Chrome, it's More Tools -> Developer Tools (Control + Shift + I).
I got the same issue and pasted the console into this pastebin: https://pastebin.com/m2XRCjru
Hopefully that helps with a fix.
It happened when I clicked continue to get out of the shop and to the next stage, the shop overlay did not disappear and I could keep clicking continue. In the background I saw new bigger dungeons being loaded until the nothing screen showed up. Also I was able to click the tiles in the dungeon in the background of the shop which was a bit weird.
Here's my inventory ah the time