It is normal to find instability in one game and not another. I assume it's just the way the game uses the card that pushes it differently than others.
Also, just because its "stable" doesn't mean that its performing at its best. Especially with DDR5, you'll want to test its performance as you increase the frequency. DDR5 has some error correction, and when you first start going past stable, it will still run, but it'll be at a reduced performance due to the error corrections.