Even with the best patch, Disc 2 is finicky. Here is what to watch for:
Grand Edition is the definitive version. Released only in Japan, it rebalanced the original game, added new monsters (such as the powerful Tiamat and Bahamut), introduced new knights, and—most importantly—split the game into two discs. brigandine grand edition disc 2 english patch
If you want, I can produce step-by-step commands for applying a common patch format (xdelta/BPS) to an ISO, or summarize a specific patch's instructions if you provide its name or a link. Even with the best patch, Disc 2 is finicky