Everything here makes sense. Once you have checked it all: the set-up, cleaned the lp's, and done all of that, there is only one thing left: maybe the records themselves are played out or poorly recorded. I have noticed that many lps I get are dead, many in the way you described.
NOTE: I also have an LP12 too and love it. I have found that it is not really very finicky (like my old SOTA), but needs to be tended by an expert.
NOTE: I also have an LP12 too and love it. I have found that it is not really very finicky (like my old SOTA), but needs to be tended by an expert.