Hi Beau,
Going from missing 3 in LR to missing 11 is definitely a big swing. While some variation is to be expected due to the difficulty of the questions, the specific question types, etc., that big of a change is fairly unusual.
The first thing to check is whether you notice any pattern to what was different between the 2 sections. Did the section where you missed 11 have more unusual or difficult question types or elements? Were the questions just statistically more difficult? Was something different about you when you took that section? For example, were you ill or especially tired, etc.?
Because you were able to fully understand the correct answers during review, I suspect that the issue is specific to taking practice tests under timed conditions (such as loss of focus, fatigue, test anxiety/rushing, etc.) rather than a lack of understanding.
Unfortunately, it is quite common for many students to panic and throw everything that they've learned out the window once they are under the time pressure of an actual LSAT test. In other words, all of the strategies that they've learned when practicing untimed (such as analyzing the stimulus, identifying the conclusion, diagramming conditional reasoning, etc.) disappear under timed conditions.
If you ever notice this happening, try to follow the proper steps to do each question, even if that means that you don't finish every question. On a related note, if you are having trouble finishing the section while doing the questions correctly, that usually is just a matter of additional practice. Focus on accuracy/understanding first and the speed will follow in time.
As to observation that you are often down to 2 answers, that is quite common for many LR questions. The test makers often include 1 very tempting wrong answer in some of the harder questions and people often evenly split between the right answer and the tempting wrong answer.
We have a podcast episode (Episode 66) on this very topic that I'd recommend you check out.
https://www.powerscore.com/lsat/podcast/66
