While playing the Sol Platinum hack, I discovered a few major bugs that ruined an otherwise well-done game:
The Seel/Dewgong line had a movepool glitch at level 65; the player gets stuck in an infinite loop of attempts to learn glitch moves.
Legendaries from Generations I-III appeared multiple times; in my first game, I caught Celebi and the Lati@s twins three times each. Not just battled them, but caught them...
Since the original hacker is no longer active, I've thought of trying to fix those two bugs myself. How easy would this be for an absolute beginner with an editing tool like PPRE?