Final gravity problem?

I brewed a Belgian ale last weekend see recipe below:

BIAB
3.8 Gal batch
8 lbs 8.0 oz Pilsner
12.8 oz Pale Malt
6.4 oz Cara-Pils/Dextrine
12.0 oz Sugar, Table
1.00 oz Styrian Goldings
1.25 oz Saaz
2.0 pkg Trappist High Gravity (Wyeast Labs #3787)

I step mashed (first time) and hit 1.082, cooled to 68F and pitched both packs of yeast (activated and fully expanded). Fermentation went crazy first 3-4 days, I almost needed a blow of tube. Bubbling stopped a few days ago so I checked my SG today and it is siting at 1.030. I was thinking I'd be down around 1.018.

Any thoughts? Should I pitch more yeast? I have a pack of S-04 sitting in my fridge. This is twice I've missed my FG this month. My hydrometer is reading correctly.

What were your mash temperatures and mash steps? Is your thermometer properly calibrated?

I would let the beer free rise and see if your gravity drops any more. It's not uncommon for yeast to slow down and not fully attenuate for a week or more, especially on high gravity beers.

Yeah, meant to ask about mash temp too.

You're at about 64% attenuation. You could try rousing the yeast. I've had good luck with that. It's only been a week though. RDWHAHB. It should finish up just fine. Some yeast just coast down through the last 10 points

I've only used 3787 a couple times and it wasn't recently but I don't recall having problems with it finishing. You should be able to get to your target FG.

WY3787 is slow to finish. Give it at least a couple more weeks to finish. SG would drop further if mash temps were good.

Seconding letting it get a little warmer.

Thanks all. My mash temps were as follows right from beersmith:

Acid Rest Add 23.50 qt of water at 95 F 5 min
Protein Rest Heat to 125 F over 15 min 125 F 15 min
Saccharification 1 Heat to 145 F over 11 min 145 F 45 min
Saccharification 2 Heat to 161 F over 9 min 161 F 30 min
Mash Out Heat to 172 F over 6 min 172 F 10 min

I EBIAB with a recirculating mash and a PID controller, I'm sure I hit these numbers. It was my first time step mashing, I may not do it again... Maybe I should have just mashed low around 148F and went with that? My Scottish Ale that I bottled today finished at 1.019 from SG 1.052 after 22 days with Wyeast Scottish Ale yeast. I was planning to hit around 1.010, that brew I overshot my mash temp of 152F up to 158F in the first first 10 mins due to not autotuning my PID. I removed lid and let cool down to 152F and finished my mash. I guessed that that would give me more unfermentables. It is slightly on the sweet side but just barely, I think it will be alright once carbed.

You know, I just thought of something. My PID temp probe is in the tee fitting on top of my mash tun lid and reading my recirculating wort temp, not actually the temp in my mash tun. There is about one foot of silicon tubing from pump to tee fitting/temp probe. I wonder if my temps in mash tun are actually higher giving me a less fermentable wort? This is only my third batch on new setup.