The craziest error I’ve ever seen was Rush’s 2112 was correctly labeled on one side, and on the other side had a label for Bachman Turner Overdrive. The vinyl was correct, just the label was wrong.One of my more fun experiences returning an album was Pink Floyd's "Ummagumma". That's a 2 LP set, one LP live and one studio. I got a copy with both LPs the same, but the second LP had the correct label for the studio LP. Since the number of tracks on each LP were different, it was obvious by looking at them that the two LPs were identical but the the salesman wouldn't take my word for it. He had to play it for about ten minutes needle dropping through the long jams before he was willing to agree that both LPs were the same!!!!
A decade later I had the exact same problem with a James Brown live set, both LPs were the same. The store owner opened another copy to see if it was OK and sure enough her entire shipment from the label was incorrectly pressed.
My copy of Love's "Da Capo" is marked mono on the cover but came with a stereo LP inside.