RCA produced at least one other item that suffered from the same problem:
the set of Rachmaninoff's "complete" recordings. About three years ago, on
finding that my copy was affected, I gave the discs a gentle cleaning with
dishwashing liquid and lukewarm tap water. They still play perfectly, and I
see no evidence that the "frosting" has returned. YMMV, of course, but
there's one data point.