Over the past monthish I've had a pi-hole running, I've noticed that at random, some websites I try to load will time out when going through the pi-hole on the first attempt, and load just fine a few minutes later.
This is especially common with sites I have not visited before and are not in the pi-hole cache. Pi-hole seems to often fail these lookups, but it suddenly works several minutes later?
I have it set to use google DNS, and I'm using the default ad lists.
I've been having a lot of trouble tracking down this problem, because it seems to only happen once and only on websites I haven't previously visited. My network did not have this behaviour before I installed the pi-hole.
I don't know if it makes a difference, but I'm using a RasPi B.
It's especially been a problem with some iPad tv streaming apps (mostly Sportsnet Now).
For an example, I just restarted the pi-hole, and then pi-hole.net would not load. I had to set my computer to use google DNS directly to make this post.