Hello,
I believe I found a false positive in Legal.exe's Sync checking, I was RNGing an appropriate Registeel earlier today and after done noticed it shows up as Sync: Invalid, to verify it wasn't something weird with the Registeel I RNG'd something more common with the same PID/IV combination and indeed it shows up as Invalid as well, the specific spread was:
PID: 30742070 (CAREFUL, ability 0) 31/31/31/30/31/31 (Seed: a00802d4 Method 1: 252, J (synch): 239, J (no synch): None, K (synch): 239, K (no synch): None) HP ELECTRIC 70
(the PID's in Hex and IV order is HP/Attack/Def/Sp. Attack/Sp. Def/Speed. </obvious_note>)
which is possible to hit with Method J with a Careful Syncer as the spread details mention.
pkm file and screenshot attached.
634158374042995000_Pikachu_247996753.pkm