what are some causes of under attenuation?

After 15 batches, I have my first batch that missed the yeast's attenuation range (got 62%, range min is 68%). Maybe or maybe not also important, it was all my first all-grain batch, and I didn't get great efficiency (~50%).

At any rate, I'm curious to learn what some causes of under attenuation are, so I can figure out if I did something wrong or not. Are there things under my control that affect attenuation?

The beer tastes great, so I'm happy with it, but due to my efficiency and under attenuation, it's only going to be 3% ABV. I guess that just means I get to drink twice as many each night

What was your OG and FG? also what temp did you ferment at?

1. Underpitching
2. Aeration/oxygenation
3. Temperature
4. Amount of unfermentables

Not necessarily in that order.

ive had underattenuation that I know was due to a temp drop at high krausen...

OG was 1.04, FG was 1.14. I think that makes my attenuation closer to 65% not 62%, but I still have the general question. Fermentation was mid 60's (65-68).

I made a starter of wlp004, before pitching, so given my low OG, I'd be surprised if I under pitched.

Aeration I suppose is a potential point - I don't really do much to aerate, aside from that when I pour in the wort I pour through a strainer, and I shake the carboy up a bit during the process... although for this batch I didn't spend as much time on that step as normal. Hmmm...

What sorts of things control the amount of unfermentables? For example there was 12-16 ounces of espresso in there, would that have an impact in a 5 gallon batch?

Keep in mind that the attenuation listed by the manufacturer is optimal. When I started oxygenating my attenuation went up quite a bit. I've heard that the fish pump with sanitary filter + aeration stone works great as well.