Date: 18 Marcheshvan 5566
From: Rabbi Moshe Sofer
To: Rabbi Yitzchak (Eizik)
A scribe wrote an entire Sefer Torah with zayin and nun peshutah strokes extending from the side rather than the center, and with yudin resembling lamed. The Chasam Sofer rules all these defects invalidate the Sefer Torah, since any significant deviation from the accepted letter form renders it pasul, whether or not the result resembles another letter. For correction of yudin within divine names, he permits scraping away the excess to leave only the dot of the yud, then adding the proper kotzin.
Source: Shu"t Chasam Sofer YD §269