Aside from the meat, the other issue here is that there is a cognition factor.
What I mean by that is you are always going to remember that first brisket that met your ideal of what a good brisket should be. What may be happening here is that you've elevated that finished brisket in your mind to something that you may be achieving again with the more recent cooks but you can't put it at the level of your first..
Every attempt is different.. different ingredients, controllable and non controllable variables etc. Better to appreciate each cook for what it is than trying to chase something that may not be realistic.
XL BGE (#2) & Performer Platinum
Former owner: Jambo Backyard, Klose BYC, Lonestar Vertical offset w/ Insulated Firebox, Medium Spicewine, Pitts & Spitts, XL BGE (#1) & (2) Medium BGE's, 22" WSM & (2) 18" WSM's, 18" & 22" Weber Kettles