Viewer crash while reading

[Dan__]

I was reading an epub on my mac (Catalina). When scrolling the text to the next page I got:
calibre, version 5.34.0
ERROR: Error in message handler: Unknown error

Traceback (most recent call last):
at IframeClient.handle_message (userscript:viewer.js:16757:21)
at IframeBoss.display (userscript:viewer.js:26831:25)
at finalize_resources (userscript:viewer.js:17298:33)
at add_virtualized_resource (userscript:viewer.js:17205:38)
at JSON.parse (<anonymous>)
SyntaxError: Unexpected end of JSON input

After dismissing the error it says:
"Loading the next section from the book (Common Sense by Thomas Paine)... please wait...

But that's all. The wait appears to be infinitely long.

And no, it does not seem to be reproducible.

I'm submitting this in case it adds any useful information to any issue that may have already been raised.

Thank you