In my latest reading of volume 4 of John Meier's A Marginal Jew: Rethinking the Historical Jesus, Meier talks about Mark 7, in which Jesus discusses such issues as defilement, clean and unclean meats (depending on how you interpret verse 19), and how the Pharisees made gifts or vows to God (qorban) so they could avoid honoring and supporting their parents.
Meier thinks that Mark 7 is drawing together a variety of traditions, since it is about so many topics. He does not think that the historical Jesus declared all meats clean, for that is not multiply attested, plus the early church did not appeal to Jesus' statement in Mark 7 in its debate about the circumcision of Gentiles entering the church. Clean of unclean meats were relevant to that issue because that is one thing that separated Jews from Gentiles. Why was that even debated, if Jesus already declared all meats clean? Moreover, Meier notes, the Jewish leaders in the narrative are not shocked by Jesus' declaration that all foods are clean, even though they were on his case about lesser things that he did. For Meier, Jesus' statement in Mark 7:19 was devised by the early church to reaffirm a church belief that certain Jewish food laws were null and void and could no longer separate Jews from Gentiles.
Meier thinks, however, that the part of Mark 7 about qorban may actually go back to the historical Jesus. Did the Pharisees really believe that Jews could make vows to avoid supporting their parents? Meier believes that there was debate about vows within Judaism around the time of Jesus. The Damascus Document 16 appears to criticize "vowing one's food to sacred use in order to keep it from a neighbor in need" (Meier's words on page 379). Mishnah Nedarim 5:6 talks about "an elaborate subterfuge" that a man had to undergo to circumvent "a vow that prevented his father from receiving any food from him" (Meier's words on page 381). And Philo in Hypothetica 7:3-5 "takes a strict view of the irrevocability of a vow, even when it works to the detriment of one's family" (Meier on page 381). Meier does not seem to believe that all Pharisees thought one could use qorban to circumvent helping one's parents, but the fact that there was debate around Jesus' time about this issue demonstrates (for Meier) that Jesus was probably addressing a real problem and that some Pharisees held the view about qorban that Jesus was criticizing.