As every other game, Terranigma has got it's own set of bugs. These are the ones I have been able to find:

The chest bug:

You need an emulator to ponder this one. In the woods northwest of Nirlake, where you get the logs from the Gumin monsters, there is a hidden treasure chest to the right of the entrance. Use the ZSnes/Snes9x sprite control to turn of a certain background and you'll see it. Now this is a curious one. You can go right up to the chest, but for some reason - it won't open. There is also another chest in grecliff, just left of a cliff with a cave entrance. It looks like it's closed, even if you have opened it.

The frozen bug:

Sometimes the game freezes at some places. The most common ones are:

I know there are more places, but they happen more rarely. If the game freezes, check if you have enabled sound on your emulator. If not, enable it, and that should solve the problem. However, this can occur on the real cartridge (atleast the PAL version) as well. If it does, try letting the Snes rest for a while and then you'll be able to proceed (usually).

The infinite money bug:

When you're having the code for infinite money on, you can't stay at inns or buy apples, flowers, lottery-tickets and other things that is being sold at "individual" shops. If you have to stay at an inn, simply turn the code off and go kill some guys to get money. It's not that hard, since three badies (at most) will give you enough.

That's all I can think of right now. If you've found out any other bug, let me know and I'll put it up here.