Is it the roaming latias or the enigma stone one in pewter? If it's the enigma stone one the NPCs are most likely messing your frame up. Post the exact calls you get from elm the next time you try, along with the nature and IVs like you did this time. 10 may be too low a frame but we'll see after the next trial run(remember to mash into the menu and mash out to encounter latias