Yes, it is something one has to anticipate, if you leave a menu, or open another, it will alter the position or the address where the value to be modified is saved, that is why you must look for pointers and see which one is maintained during most of the game.If you can't hack a value it means you didn't find the correct address. Did you try all the common data types? Always search with u32, f32 and f64 before giving up. What you see on screen may be a cached value, it is not uncommon that the correct address when hacked don't change the display until the game actually have the value updated.