→Safek Derabbanan Lkula - Safek Eched Deoritta Safek Eched Derabbanan
# The Gemara Pesachim 9a implies that a case where there’s a doubt if it was checked for chametz and additionally there’s a doubt if bitul chametz occurred it must be checked again. That seems to prove that it isn’t a safek safeka and is forbidden. The Rashba answers that chametz might be more serious than other prohibitions. The Tosfot HaRash Pesachim 9a answers that the case was where there was no bitul. They’re both assuming that we would apply safek safeka in such a case.
# Do we follow that answer of the Rashba or Rash? Locally in Brachot 31a this question which the Rashba was discussing affects a case of food brought into the house unprocessed whether it is exempt from trumah altogether. The Gra YD 331:84 writes that we follow the strict opinion in that discussion and accordingly we’d be lenient to consider it a safek safeka. Rav Chaim Kanievsky in Derech Emunah Maaser 3:63 holds that the Rambam is lenient and if so we’d be strict about the safek safeka.
See Shach Klalei Safek Safeka YD 110:16 who says it is a safek safeka. Rabbi Akiva Eiger OC 184 says it about birkat hamazon for woman.
==Safek Safeka With Kulot that are Soter One Another==