Re-circulation can help with extraction, but extraction in the mash has a lot of moving parts. pH plays a huge role, temperature obviously does as well as time. It's also good to know how to target the two main amylase enzymes, beta. and alpha. Each of these enzymes require a different temperature and pH. Generally a lower temperature (143-148F) and a pH of 5.0 to 5.4 will favor the beta enzyme, giving you a more fermentable wort. At this temperature the mash needs to be extended (90-120 minutes) because the beta enzymes require more time to complete the conversion.
The alpha enzymes are targeted by higher temperatures 150-162F and work better when the mash pH is between 5.4 to 5.6. Alpha enzymes produce a less fermentable wort because the resulting sugars are more complex. This also means faster conversion due to "easier work" and the higher temperature which speeds up the chemical process. When I brew I target both to a degree. I lean toward the beta when I want a dryer beer and I lean toward the alpha in less dry beers. This is why I step mash. Start out low for beta and raise the temperature to get some dextrins for some body. pH is sometimes a compromise between the two.
With extraction that low, it maybe that temperature and the grain/liquor are not equal mixed throughout the mash. Some grain could still be trapped in a thick "dough ball", while others are like soup. This keeps not only the temperature uneven, but also the enzymes are not distributed evenly and may even be trapped in the "dough ball". pH is also uneven and acid additions don't get mixed in thoroughly.
Most of these problems could be fixed by re-circulation, if that's your problem.