I had a bunch of different 15 bobbins and used them in my 237, some fine but what I found was they would also, some of them, pop up and wouldn't seat on the winder post and also a bunch of them wouldn't even fit on the post the dimensions were wrong. Those were just a bunch of bobbins I threw into a bowl when I ran across them so some are newish and some are older, so I am thinking the problem ones were newer. So I had to go through and test each one on the post and separate them. So buying good bobbins is so very important.