fermentation slow to finish

I've got a beer that isn't fermenting out all the way, at least not quickly. This one is an IPA - mashed at 153F. I had a mash-out problem - I hit my 170F mash-out, but then the false bottom run-off tube clogged and it took 45 min to get it all fixed, including dumping to a 2nd vessel, fixing and returning. By that time, it dropped to ~125F. The pre-boil gravity was ok, I was still at 74% efficiency. Yeah...HSA might be there, but nothing I could really do about it.

I hit the fermenter at 1.062 and a week later it isn't moving past 1.020/21. According to Beersmith, I should be hitting ~1.017 for the minimum of 73% attenuation for this Wyeast 1335. I used a 2L yeast starter, pure O2 in the fermenter for 90s and the fermentation took off like mad. I had ~3h of lag until airlock activity, and on day 2 had around 4" of foam in the primary. It slowed down after ~5 days, then I racked into the secondary. The secondary fired back up a bit, bubbling about once every 3-4 minutes, but nothing major. There is a bit of head around the edges, but nothing significant.

Temps: controlled fridge from 69F to 71F.

Where to go? Do I pitch a 2nd hit of yeast (something neutral?) or do I just move on with the dry hopping and live with it being slightly sweet ?

Also - where am I going wrong to get into this spot ? Mash too short? Impatient ?

I had a similar problem myself and from the research I have done, I would make the following suggestions: 1. You may have racked to the secondary too early, and I suspect you limited your ability to get it to ferment further. 2. If it seems like the yeast is stalling, you can try giving the fermenter a gentle swirl and maybe raising the temp a few degrees. You can probably pitch a second yeast, but I would suggest making starter first if you do so the yeast is prepped for the alcohol, but I think given the difference between your gravity and the one you're looking for it seems like it might be a bit of a waste. My suggestion is next time try my second suggestion while it's still in the primary. *Edit* Also a yeast energizer might be helpful in the future if you get stuck in the primary as well.