What method were you using to determine the wildcard was special attack? If it involved pokemon with a different gender ratio than kangaskhan (100% female), i believe the ratios were thought to affect inheritance earlier in this thread (though it may have only affected gender and ability). You could try doing the same thing with a different pokemon and comparing the resulting spreads.
I did last night just to be double sure, I put in two Solosis for an inheritance of everything but Attack, and it came out 4 IV's instead of five. I can update saying I used a shitty wildcard to see if things somehow worked themselves out, and did it with my 6 IV'd Volcarona (31/31/31/31/31/31) and 5 IV'd Ditto (31/X/31/31/31/31) on an inheritance that lacked Defense and I got the 5 IV's. Plus I'm not sure if the other people above were trying to breed Kangaskhan/other gender ratio Pokemon (100% female/100% male) or not. But it did happen with the Solosis as I said and it's a 50/50.
Also here's what I've been doing since I started using this whole Pseudo-RNG method:
1. Put Magikarp-m (Everstone) and Magikarp-f (Destiny Knot) in Daycare.
2. Run around till egg is generated.
3. Reject egg and save.
4. Repeat 2.
5. Accept egg and fly to Lumoise.
6. Hatch egg, take battle test and take note of inheritance.
7. Reset and replace with appropriate parents.
8. Repeat 2 and accept egg.
8-1. Save Game if 5 IV Pokemon is desired shiny via Instacheck.
9. Fly to Kiloude, hatch egg and check stats.
This has 100% worked for me fine till last night. :/ I literally have these sitting in a box and I'm 100% positive their IV's are correct, they're kind of just waiting to be hatched shiny.
Egg #1 (Dratini - Jolly - 31/31/31/X/31/31 - SV = 3070)
Egg #2 (Deino - Timid - 31/X/31/31/31/31 - SV = 228)
Egg #3 (Dratini - Jolly - 31/31/31/X/31/31 - SV = 3448)
Egg #4 (Larvesta - Timid - 31/X/31/31/31/31 - SV = 1548)
Egg #5 (Gligar - Impish - 31/31/31/X/31/31 - SV = 3653)
Egg #6 (Drilbur - Adamant - 31/31/31/X/31/31 - SV = 2398)
Egg #7 (Bagon - Adamant - 31/31/31/X/31/31 - SV = 3551)
Egg #8 (Solosis - Bold - 31/X/31/31/31/31 - SV = 2652)
Egg #9 (Rotom - Timid - 31/X/31/31/31/31 - SV = 3052)
Egg #10 (Squirtle - Modest - 31/X/31/31/31/31 - SV = 3321)
Egg #11 (Charmander - Timid - 31/X/31/31/31/31 - SV = 3314)