quite often visiting the manufacturers web site is a good idea- they generally have a link for 'corrections' for all of their patterns.
often the fabric manufacturers have someone who uses a software program and puts together a quilt pattern to 'compliment' a fabric line- people then download those free patterns- it is only after a few have started (trying) to put them together that the errors are found- then they are listed on the 'corrections page' of the website. fabric designers are often not quilters