ok after you sew your blocks together each individual one before you sew them to the next one are you squaring them up? this is your issue I think. Square each block up, after you sew them together so they make the right size for the block your doing in the end ie four patch across down is 3.5 each square. the three across is 4.5 and sew on. even with my stupid quarter inch foot I still have a bit of trimming to make those blocks square no idea why either thought it would solve all my troubles ..
glad you have found the right pattern did you tell the people that there is an error or check to see online if there was a published fixed pattern often they do that put the correct measurements up as a sorry here are the ....online for you to use. frustrating to say the least. pretty pattern however.