eFootball Friend Match Network Error C_NAJM_0028 Despite Good Internet

I was playing the eFootball mobile game with my friend today when the game suddenly disconnected, even though my internet connection and ping were perfectly fine at that moment. Since then, I have not been able to connect properly to friend matches. When I try to play, I receive an error message saying “A Network Error Occurred” with the code “An invalid command was detected. KODE::C_NAJM_0028.” This situation only occurs in friend matches, not in every mode, which makes it even more confusing because my connection appears stable. I would like Konami to clearly explain what this specific error code means, why this problem occurs even when my internet connection is good, and what I need to do to solve it so that I can play friend matches again without connection issues.