Two of my favorite beers were Great Lake's Octoberfest and the Conway's Irish Ale, both seasonals. In 2014, I got the Octoberfest and as soon as I poured it into the glass, I knew something was off. The color was different, aroma not as intense, and the taste wasn't the same. I went so far as to email them and as I'm less than an hour away, I took a bottle up to them. Had lunch as their brewpub and even before the waiter got to my table with the draft Octoberfest, I could see the difference.
They told me the recipe hadn't changed. Something, however, did. Neither beer has been what I remember since then. They're not bad, just not as good.