You need to have at least two tiles of walkable space at both the entry point and the exit point, otherwise you'll just fall into a pit. The reason is that you're switching back and forth between tiles as you pitwalk, which makes the game try to pull you into the other pit. If there's an obstruction to where there's a pit of width 1 you can't fool the game into trying to pull you into the other pit because there is no other pit.
EDIT: I'm a complete newbie at setting up Bizhawk; when I tried to play back that file I got this:
![](https://dl.dropboxusercontent.com/u/81413272/Legend%20of%20Zelda%2C%20The%20-%20Oracle%20of%20Ages%20%28USA%29.2014-06-21%2017.58.02.png)
EDIT2: Never mind, I was using an interim build instead of the official release. Doy.
EDIT3: And as it turns out, Bizhawk's Ram Watch and VBA-RR's Ram Watch show different values for the addresses I gave earlier, so it's back to the salt mines for me. At least I have a workable test case for finding Monster 0 HP ^^;....