Just thought of another one, that happened in a speedrun of Ultima 3: Exodus on the NES (this doesn't happen in computer versions).
After you defeat Exodus, the castle will start to crumble, and you have to escape; after each step, a mountain will appear on a random square, making that square impassible. If you get unlucky with the mountain spawns, you can get trapped and unable to escape. Furthermore, you take damage with each step. So, if you get particularly unlucky, you could get through the entire castle, kill the final boss, and be unable to escape because the RNG decided to be cruel.
In other versions (other than, I assume, the MSX version which is based on the NES version), the game ends immediately after you defeat Exodus, so this problem can't occur. Of course, bad menuing could still cause you to lose the game at the last moment, but that's another story entirely.