Yeah, something is going on with GP's browser. I have Fastmail open in Firefox right now, I've never had an issue with it.
I'm not saying that to dismiss the problem, I believe GP that it's crashing; more bringing it up to say "there is something going wrong here that's not at the browser/site level that could potentially be fixable for you on your local device if you want to use Fastmail in Firefox."
I'm not saying that to dismiss the problem, I believe GP that it's crashing; more bringing it up to say "there is something going wrong here that's not at the browser/site level that could potentially be fixable for you on your local device if you want to use Fastmail in Firefox."