Here are my sources:
Lost Media Archive: The Price is Right (Missing 1970s-2000s Episodes)
TV Tropes: Missing Game Show Episodes
Here is the part from Lost Media Archive:
"What are missing are episodes that had mistakes take place. The third episode ever taped for the daytime revival in 1972 never aired due to a contestant being ineligible and playing anyway. The third episode of the syndicated nighttime run, also taped in 1972, was never aired due to a special set of calculators they used for the show malfunctioning. Two more episodes, taped in 1976 and 1978, were never aired for unknown reasons. On June 8, 1988, production stopped when Janice Pennington got hit with a camera, completely knocking her off the stage and broke her collarbone. As a result, she no longer wore swimsuits on the show. In 2001, yet another episode went unaired due to two contestants switching places in order to cheat. It is not known if any more episodes like this exist or what has become of these other ones. None of the ones mentioned in this paragraph have surfaced."