Long waits for Firefox and SeaMonkey to respond to links from other applications

[Kjell Tore Ullavik]

On 24.03.2019 17.25, Graham Perrin wrote:
> When I open a web address in (for example) Thunderbird, there's a wait 
> of around fifteen seconds before the web browser, already open, 
> handles the address.
>
> Affected browsers:
>
> - Firefox
> - SeaMonkey
> - Waterfox.
>
> Not affected:
>
> - New Moon (Pale Moon) – the waiting period is a split-second
> - Chromium – split-second
> - Falkon – less than two seconds.
>
> Any ideas?
>
> <https://put.re/player?id=b62zHf8k.m4v> shows the waiting period with 
> Konsole as the starting point, Firefox as the default web browser.
>
> I can't say exactly when the problem began, but it was long before 
> Firefox 66.
>
> ----
>
> $ date ; uname -v
> Sun 24 Mar 2019 16:23:22 GMT
> FreeBSD 13.0-CURRENT r345330 GENERIC-NODEBUG
> $ pkg query '%o %v %R' firefox seamonkey waterfox
> www/firefox 66.0_3,1 poudriere
> www/seamonkey 2.49.4_24 FreeBSD
> www/waterfox 56.2.7.2 poudriere
> $

I have seen this as well. But not right now so can't investigate.
Could it be a dbus problem?

I also have a vague and incomplete memory of fixing a similar
problem a long time ago by filling out my /etc/hosts.
Though that seems a bit weird.