Hello:
I have also had problems with FireFox crashing with JAWS 2020. I kept
JAWS 2019 on my system and tried it and JAWS 2019 crashed with FireFox on
the same site.
A site that has always crashed recently is: https://cvstats.net/
I started the latest version of NVDA and the site didn't crash.
Hope this helps.
Regards,
Robert