The opponent is still in a juggle state after being dizzied during a juggle in both Rebalanced and Custom. Like hitting them with any normal that doesn't knockdown after they are dizzied during juggle will cause them to fall into a knockdown instead of being in a standing hitstun.
Simple corner combo into dizzy using Custom Aquaman. (https://gfycat.com/DigitalEagerHermitcrab) Interested on how you approach the others if you do keep the same scheme of Source/Rebalanced/Custom.
Oh also as a test I deleted everything in Aquaman's Statedef -2 and Statedef -3 and the bug stops happening so maybe it's there?