I think your problem is that in all the IV spreads your using, none of them have a perfect IV stat in Sp. Atk. (I think it's Sp. Atk, anyway)

x/31/31/**x**/31/31

31/31/x/**x**/31/31

x/31/31/**x**/31/31

31/x/31/**x**/31/31

If the order you presented is correct and such, then yeah, there's one of your problems.

The remaining IV that isn't perfect is probably just the result of bad luck. Sorry. :(

Hope I helped. :)