The November 1942 issue of SPICY MYSTERY STORIES was mis-labelled as volume 12, number 5, when it should have been volume 12, number 6.  This was corrected with the December 1942 issue.  This sort of mistake was fairly common with some pulp chains, particularly Fiction House and their title JUNGLE STORIES, but perhaps the most egregious example of this sort of mistake occurred with SHORT STORIES, which also identified each issue by whole number.  The December 10, 1948 issue was whole no. 1029, but the December 25, 1948 issue was mis-labelled whole no. 1930!  This mistake was never corrected, with the result that, from that point on, each issue was labelled with a whole number 900 issues higher than it should have been.