I do not know how many UD screwed up. I have the same card as you with Vaughn on front and Boggs on back. I also have Biggio with Roberto Alomar on the back, Maddux with Carl Everett on the back, Steinbach with McGwire on back, Chili Davis with Molitor on back, Matt Williams with Ozzie Smith on back and maybe a few others. They're just oddballs in my player collections. I wouldn't consider them part of the set. Misprints are mistakes. The same as getting a card that's missing the foil stamping on it or miscut so badly that two players are showing. They weren't "intended" to be part of the set.
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