Stalled Fermentation?

[BeerBreath]

First post on HBT after months of lurking! Even without posting, this site has helped me out a ton in the 5 months I've been brewing. So thanks everyone!

I brewed my 8th batch (5th all-grain) on 9/13: BierMuncher's OktoberFAST ale. My gravity has been stuck at 1.020 for at least 4 days now. That's not unreasonable for an Oktoberfest, but at only 66% attenuation it's lower than White Lab's given attenuation of 72-78%. Here's the nitty gritty:

-Here's the original recipe. The only modification I made was to scale it down to a 5 gallon batch. I do BIAB with a simple 1-2 gal sparge just slowly poured over the bag.

-I didn't adjust grain weights for efficiency, so I overshot my OG by a bit (1.059, recipe's OG is 1.051).

-Mashed at 156F (fell to 151F after 60 min) to keep the FG a little high.

-I used WLP029 kolsch yeast. I did a 2 step starter because the sample in my yeast bank was awfully small (maybe 15 billion, rough estimate). Started with a half liter, then another 1.5 liters added on top 3 days later. The layer of yeast at the bottom looked as thick as previous starters I've made, but this was actually my first time reusing banked yeast or making a step starter. I also aerated with an aquarium pump and air filter for 15 or 20 minutes before pitching the yeast.

-I have a chest freezer + heat pad + Inkbird. I started fermentation at 58F and ramped up to 65F over the first 3 and a half days. I took my gravity reading on day 5 (hydrometer, not refractometer). Seeing the high reading, I raised the temp 3-5 degrees every 1-2 days, taking gravity again before changing the temp. As of today (day 9), the temp is all the way at 76F and gravity is still sitting at 1.020. I also used a long sanitized spoon to gently stir all of the yeast and trub off of the bottom today.

-I bottle condition, which is the real reason I'm bothered by all of this. I'm worried that the priming sugar will be what finally wakes these yeast up again, and all of my beers will be gushers, or worse, bottle bombs.

(If I left anything important out, let me know)

So what do you all think? Is my fermentation stalled, or did this batch just finish kinda high? Unless I'm doing the math wrong, 72% attenuation would only be 1.016 or 1.017. It doesn't taste all that sweet, but we're only talking 3 or 4 gravity points. Maybe the yeast were extra tired after doing the bulk of their work in the cold, combined with the hot mash, and fermentation has been finished for days?
After a little Googleing, other people have had stalled fermentations with WLP029 if the temp is under 62F. Maybe I didn't warm it up fast enough?
Assuming that stirring the yeast and raising the temperature this morning didn't kick things off again, should I play it safe and go out and buy a packet of S-05? Is there anything else I should do, or am I making a mountain out of a mole hill?

Thanks all!
I'm about to leave for the Great American Beer Festival tonight, so no one take it personally if I don't respond until tomorrow .

 

[JohnSand]

Welcome aboard! Your steps seem thorough and proper to me. I've occasionally had a batch finish high without trouble later, I think you'll be okay. I do remember that last time I fermented a lager, it seemed to finish high. Then I realized that it was tiny bubbles of CO2 sticking to the hydrometer. I suspect that the cooler ferment let the finished wort absorb more carbonation than I'm used to.

 

[eric19312]

At 76F I can’t see you getting more attenuation out of the current yeast. I’d call it done and package and drink soon. I’m worried you have been messing with it too much, between sampling and stirring you are probably introducing oxygen. That might shorten shelf life which is why I’m suggesting drink it soon.

 

[Blackdirt_cowboy]

I brewed an O’fest few weeks ago, and it, too, stalled out at 1.020. I warmed it up to no avail. I finally just kegged and carbed it up, and it is yummy. Maybe a tad on the sweet side for an O’fest, but bready and malty none the less. I say bottle it up and enjoy it. It will probably be delicious.

 

[BeerBreath]

Thanks everyone!

I think stirring restarted the fermentation, it's bubbling slightly faster (1 bubble / 18 sec today vs 20 seconds yesterday). I know that's a pretty poor way to guage activity, especially after stirring the beer, but as Eric pointed out I've already opened and closed the fermenter more than I should. I'll need to do one more sample for gravity, maybe two if it did restart, before I bottle so I'll get proof then.

Per everyone's recommendations, I'm not going to add more yeast or mess with the temp any further. I plan to just say a quick prayer to the beer gods before bottling this batch up later this week.

Cheers!