As far as I know, the GMAT does not specifically penalize you for getting multiple questions in a row incorrect.
In fact, if you have to guess at a couple of questions in a row there is a good chance that you will either get one of those correct via a lucky guess or one of the questions will be a "non-scored" experimental item.
The reason that a person's score declines more when they get multiple questions wrong in a row is that when you miss several questions in a row (and I do not think that two counts as several - I am thinking more like 3 or 4 at least) there is a very good chance that at least one of these questions is an easier question.
The effect of missing several questions with at least one being a lower difficulty is cumulative and results in the computer downgrading not only the difficulty of the future questions that you will receive but also lowering your score.
Ironically, given your worries, perhaps the best place to miss two or three in a row may be at the end of the test - GIVEN THAT YOU HAVE BEEN DOING WELL UP TO THAT POINT.
The real danger of guessing at the end of the test comes when you have been rushing and then guessing. A situation where you either miss or guess at 6 or 7 of the last 10 questions. If that happens the cumulative effect creeps in and the questions that you guess at at the end will be lower difficulty questions. If you are going strong and then guess at the last 2 or 3 this should have little impact since these questions will hopefully be at a higher level of difficulty and less harmful when missed.
You can read more about it in this article that I wrote for the Veritas Prep blog. https://www.veritasprep.com/blog/2012/12 ... -the-test/
