Since I use naphtha in my STB extractions I run across the following problem: There is a lot of solvent getting trapped in the base-solution. On an 270g MHRB extraction I did 4 pulls (3x 70ml + 1x 120ml) but in the end I only got about 60ml milky solvent. What happened to the rest?
I mix the jug carefully so no emulsion occurs. The two layers separate clearly. After one hour sitting in a heat bath I pour the base-solution into a bottle with a thin neck for siphoning. But with every pull there is only a thin layer that's equal 1/3 of the solvent used in the bottle and after decanting the fluid two times there is almost no solvent-layer in the big jug. What happened? Never had these problems with toluene.

Evaporation ? As Naphtha evaporate much more easily than toluene.

During heat bath (temperature ?) do you keep the cap on the bottle ?

During the heat bath I keep the lid slightly open to release the pressure that builds up. Can't imagine that such a big amount evaporates so fast. I immediately pour the solvent out into a mason jar.
Yesterday I noticed gas coming out of the jug in the heat bath. The boiling point of my nahptha is around 50°C. So today I decreased the Water temperature to 40-50°C, which should be alright. But there's still about half of the solvent trapped.

If you keep the jar in heat bath for 1 hour at more than 50°C, a lot can vaporize (my naphtha boil at 60°C).
btw, if you heat to much during pulls, you will get a lot of fats and whatnot. I try to stay at 40°C and not more than 45°C to get white cristals.

If your basic soup is liquid enough and there is no emulsion, i don't know how naphtha could be traped in it(i guess you use powder of MHRB).

I have let the last pull sit overnight in a heat bath at 40°C. After separating the layers there still was only half of solvent collected.

I will see what the yield will be. Maybe I got most of it any way by doing five pulls.

You could, I had the same problem with doing a STB extraction, even at room temp. Try adding a bit more basic water to it and stir.

Better solution is to an AB extraction. It's more steps, sure. But it'll save you supplies and headaches.

@Spiritofspice
I don't exactly got what you mean. How do I break the emulsion?

I got a very low yield of 1g spice. On my previous extractions following the same method with toluene I had a yield from about 1.8% There must be a lot of solvent trapped in an emulsion. Don't know what this could happen as I turned the jug upside down slowly.

Here's your problem, or most likely your problem. It's definitely a problem with a stb tek or any tek you don't filter your liquid. Most likely you have tiny bits of bark 'dust' floating at the top of your aqueous layer that's partially attracted to the organic (solvent) layer. You're just going to have to deal with it, and filter it. Be sure to rise the filter with basic water afterwords to remove any trapped goodies.

Later this week I plan on uploading a tek that involves absolutely no solvent mixing, no shaking, rolling, emulsions, long evaporations. No more of that BS. It does absolutely require a 5-10$ piece of equipment, though. But the money saves in wasted solvents and dumb turkey bastors more than justifies it.