Looks like this happens occasionally, and usually has to do with URLs in session and bookmark files, especially in non-latin countries.
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rodocop (2017)
just check there is no cyrillic URLs in sessions.json (in your profile).
This was greatest glitch of 75.x versions - they all (releases) crushed after trying to use non-latin domain URLs like роÑÑиÑ.рф etc.
In a later post he wrote this was fixed in KM76.
In much older versions, like my KM1.6, there was a similar prob with non-UTF8 encoding of macro created INI-files, if those were used to store URLs. Guess Dorian fixed that also in one of the later 7x versions.
And in a bugreport for Firefox 52 someone had the very same prob too, and figured out in his case it had to do with some problematic font in last session tabs, he could fix it by allowing
browser.display.use_document_fonts: 0 -> 1