4 Common Mistakes Made In Beer Fermentation When you get to the fermentation stage of brewing, you might think it’s smooth sailing from then on. Unfortunately, a lot of brewers make this mistake and don’t take fermentation as seriously as they should. There are plenty of reasons your beer can fail during its fermentation, and we want you to be able to avoid them. These are a few common mistakes made in beer fermentation that you don’t want to fall into.