I do not find that the LCMS claims to be infallible. However, what they say and how they present themselves are very different. "Bible" studies teach the Catechism or the Book of Concord. Ask a question about what God taught and you'll be referred to something in the Catechism. You might as well not even have a Bible because they'd have you believe everything you need to know about the Bible has been conveniently placed in the catechism where it has been reworded in a way easier to understand. Some people might call this interpreting and that is bound to include errors somewhere along the way. I like the fact that the print Bibles have been interpreted by experts from a wide variety of denominations and so the information does not reflect one point of view only. I will not use a Catechism or any other book to tell me what the Bible Believes. If the LCMS were to actually go back to teaching the Bible, maybe their numbers would climb.