I remember a friend sending me a PAL version of Azel, and I got it to boot with the Action Replay..... but only once. After that it just wouldn't work anymore and I had no idea why. My friend suspected it was because it was a multi-disc game, but I still can't understand why it worked that one first time. I had to reluctantly return the game to him without having played it.
Fortunately I got a US copy later down the line for very cheap, so it worked out.
Are there
any other Saturn games that are multi-disc, now that I think of it?