If the "Nun" preceding Bamidbar (Num) 10:35 is not upside down, is the Torah still kosher?

Question

While reading last week's parsha, I noticed that the letter "nun" immediately preceding the verse Vayehi B'nso'ah ha'aron Bamidbar 10:35 was written as regular nun (tagin on top) rather than upside down, as the majority of Sifrei Torah seem to have this. I base myself in this on my own experience as a Ba'al Kri'ah over 30 years and having seen about 200 different sifrei Torah in that time that ALL have them. (See Talmud Shabbat 115b - 116a, for the source of the symbols, though it's not apparent that the format is specifically a nun, there.) The nun after verse 36 was upside down.

Does this make the Torah passul? I am surmising that it might, because one might argue that this is like an extra letter written in the Torah, which should not be there. Incidentally, there was a space between the 1st nun and the preceding as well as the next parsha, so it did not look like it was attached to any word.

Answer 1

If the Nun's were not inverted but were left as regular letters, it is kosher bdieved.

Source: Sefer Keses Hasofer (Mahadura Tinyana), Chakira 17 (s.v. v'hinei hageonum) citing Noda Beyhudah and others (Sefer Keses Hasofer is the classic source for Hilchos Stam by Rav Shlomo Ganzfried, the author of the Kitzur Shulchan Aruch and is probably the standard text for learning hilchos Safrus.)

If the Nun's were completely left out the Torah is also kosher b'dieved .

Source: Sefer Keses Hasofer (15:8) in the name of the Bnei Yonah and Teshuvos Maharam Lublin disagreeing with Maharshal.

Here is the sefer Keses Hasofer (Mahadura Tinyana)