I've always had this multi-cart wireless problem with these two flashcarts and those specific games for a decade+, I'm today on newer sandisk SD cards and up to date verified roms and the supposed latest firmwares, but they still don't work with...
I got a couple of flashcarts and DS Lites, a Supercard DSTwo (EOS 1.14, FWUpdate 1.25) and an Acekard 2i (Akaio 1.9.0). For the most part local multiplayer between these two works perfectly. Titles like NSMBDS, MKDS, Clubhouse Games, Mario Hoops...