Intermittent temporary DNS resolution failure in web browsers

Intermittent temporary DNS resolution failure in web browsers

None of the suggested questions had these precise symptoms.
On my mid-2010 27" imac I sometimes am unable to resolve a certain domain
for only minutes at the time. Seemingly at random and very intermittent
intervals.
Which domain it is varies wildly, I believe some are recurring like
slashdot.org and github.com but I can't prove that. During these problems,
all other domains work fine.
This has gone on for years now but I'll describe just one specific
situation, the most recent one.
I go to openvpn.net in Firefox 23 Beta, it won't resolve. I immediately
recognize the problem because the chances are less likely that openvpn.net
has an actual DNS error.
So I open Safari, same problem.
I run dig @gw1 openvpn.net A and I get the correct results, IP-address as
of writing being 54.215.128.159. Also ping and host commands will work
correctly during this time of DNS resolution error.
After approximately one minute is passed, I refresh the browsers and the
domain works fine. During this time, the domain has always been able to
resolve using dig against either my local gw1 router or my ISP, or the
OpenVPN DNS host cloudflare.
Now let me explain some about my network, in case it helps.
My router, gw1, is actually called gw1.mydomain.local. I know that the
.local suffix can cause problems with mDNS. It did cause problems on my
Debian laptop until I moved mDNS down the order of nsswitch.conf.
I don't know how to do this on Mac OS but using the short names like gw1
and server2 have never been a problem to me on the Mac.
The router in question, gw1, runs OpenBSD 5 with Bind9. If I try to
remember back to when I was using the Time Capsule as a router, I can't
remember having this issue.
The Mac runs 10.7.5 and is connected over ethernet to a switch, which in
turn is connected to the OpenBSD router. On this same network is a Time
Capsule in bridging mode that used to serve as router but is now only a
bridge for any wireless device in my home.
I also can't remember having the issue on any of my other devices, being
an Android pad, an iphone and a Debian laptop. And of course other peoples
devices that were brought here.
So that's why I'm posting on this board, because I think the problem lies
in higher level DNS functions of OS X. Because only my web browsers are
being affected so far, the problem is too intermittent to know if my Mail
client is also affected since I rarely use it from home.
The .local domain should not confuse DNS resolution for the Mac since its
DNS is set to the IP-address of gw1, that being 192.168.22.1. But I can't
be certain.
Another reason that makes me more certain this problem is not related to
my use of the .local suffix for my private LAN domain is because I only
started using this suffix a few months ago. Before that I was using a .se
TLD, which I found was wrong eventually since I wanted to separate the
external domain from my LAN.
Here is an image I took of my most recent problem, it simply shows what
I've already described.