Firefox 77.0.1 (64-bit), Manjaro (Archlike linux) up to date, 16GB ram DDR3, Notebook on intel i7 6700T CPU @ 2.80GHz
Extensions: HTTPS Everywhere: 2020.5.20, Passbolt Extension: 2.13.3, ublock Origin:1.27.10, Cookie AutoDelete:3.3.1
I will include some report if it happens again.