If a p’sul is found in a Sefer Torah – does it mean that a person was not yotzi all the prior Krias HaTorah – even if may be that an entire year of Krias HaTorah has passed since that Parsha was last read and then the Torah was kosher.
Even if a pesul is found, several opinions maintain that the congregation was still yotzei the readings of the Torah. In fact, even when a pesul is discovered after the reading of the Torah is complete, one does not return to read the Torah reading again (one only reads again if the pesul is found while reading). This is because we rely on the lenient opinions (Mishnah Berurah 143:13).
Rabbi Shlomo Zalman writes (Halichos Shlomo, Adar 18:4) that this is the halachah even concerning Parashas Zachor (we are lenient based on the leninecy mentioned in the Rema 143:4).