Rav Herschel Schachter states:
. A matter of halacha which has been accepted for centuries can not be overturned, unless one can demonstrate that there simply was an error involved from the very outset.
- Rif Rambam paskened 2 matzos at the Seder as per simple read of the Talmud.
- Gaonim have a tradition for Lechem Mishnah on Yom tov
- Rosh/Tosafos say 3 - that sugya is superseded by the requirement of Lechem Mishneh
- Rema says 3 ratifying Minhag Ashkenaz
- Bet Yosef says that minhag is like Tosafot and Rosh and paskens 3 despite his stated rule re: Rif/Rambam - Minhag Yisrael prevails nevertheless
- Shleah - as cited by kaf Hachayyim says the only way to be yotzei lechal hadei'os is to use 3.
- Were Rosh, Rema, Shulchan Aruch, Shelah all beta'us?
- If so does this impact their reliability on other matters of Halachah?
- Did the Gra feel bound by the norms Minhag Yisrael - or by his read of the Talmud?
- For those who have already switched to 2, should they switch back to 3 - since the shita of 2 goes against the norms of Halachic canons as posited by RHS? ""one can demonstrate that there simply was an error" . i.e the error here is going against Minhag Yisroel.
- Is there ever a time limit on overturning Minhag based upon error? IOW how many centuries of practice makes perfect or is it ALWAYS subject to revision based upon a better read of Talmud.
- How do recently discovered girsaos of old manuscripts play into this? Are they demonstrative of earlier errors and therefore dispositive of minhaggim?
Kol Tuv / Best Regards,