The Laws Regarding If A Torah Scroll Was Found To Have An Error And Other Laws Regarding a Torah Scroll. Containing 5 Se'ifim:
We do not read from the Torah with less than ten adults who are free (ie. non-slaves). And if they began with ten and some of them left, they [continue reading until they] finish.
If each Chumash (ie. each of the five books of the Torah) was written separately, even if they were each rolled like a Torah scroll, we do not read from it until all five books are sewn together. Rem"a: And they must be rolled like a Torah scroll. But our Chumashim, even if all five books are [bound] together, we do not make the blessing over it (Mordechi - end of chapter "Hanizkin" and end of chapter "Hakometz", Teshuvot Ramba"n - siman 187 and 199, Rabbeinu Yerucham - Netiv 2, third volume, Agur - in the name of Shibolei Leket, Mahari"k - shoresh 68, and Kol Bo and ??? - chapter 9 in Laws of a Torah Scroll). And in a place that has a Torah scroll, but the prayer leader [who is reading for others] is not an expert in reading using the correct cantillation marks by heart, I saw that some have a custom that the prayer leader reads from the Chumash using the markings (ie. the cantillation marks), and the one who got called up reads after him from the valid Torah.
Even in villages that do not a valid Torah scroll, they should not recite the blessing upon [reading from] it.
If an error was found in a Torah scroll during the reading, they should take out another Torah and begin reading from the place where the error was found, and complete the number of aliyot that are left from those who already read in the Torah that had an error. And if the error was found in the middle while the reader was reading, he should finish his reading in the valid Torah and recite the blessing [that's recited] afterwards, and he should not go back and recite the blessing [that's recited] before. Rem"a: If they already read 3 verses and it's possible to stop [where the error was found], they should stop there and recite the blessing [that's recited] afterwards, and then they conclude the remaining aliyot in the other Torah that they took out (Mordechi - chapter 2 in Tractate Megillah). This that we take out another Torah is specifically when a complete error is found, but if was only because of missing or extra letters, we don't take out another Torah, since our Torah scrolls are not so precise so as to say that the other one would be more valid (Agur and Piskei Mahari"a - siman 80 and Ria"z). And Mahari"l ruled that another Torah should not be brought, and Beit Yosef ruled that another Torah must be brought (and therefore, we make the above compromise). In an extenuating circumstance, where the congregation has only one Torah scroll which is invalid, and there is no one there who is able to fix it, some say that it should be read from and the blessings should be recited (Kol Bo and Abudarham), and some invalidate it (Teshuvat HaRashb"a 487 and 405?, and Maimoni - chapter 10 in Laws of a Torah Scroll). And if one of the chumashim (books) is complete, without errors, one may be lenient and read from that specific chumash, even though there are errors in the others (Ra"n)
A synagogue that has only one person that knows how to read, he should recite the blessing and read a few verses and then recite the blessing [that's said] afterwards. And then he should repeat and recite the blessing beforehand and read a few verses and then recite the blessing [that's said] afterwards. And he should do this several times according to the number of aliyot for that day.