I'm not seeing this happen using either Browser Cache or Flaresolverr.
I'm using:
OS: Win10
Calibre: 7.2
FFF: v4.30.1
Flaresolverr: 3.3.12
"not well-formed (invalid token)" appears to be an XML parser error, judging by google returns.
Are you using a vendored version of Calibre (IE, from your OS) or the official version?
Have you put a website_encodings setting in personal.ini?
I'd also try setting continue_on_chapter_error:true
|