Unexplained Error during Play on iMAC

[Vyy]

Ever since the maintenance before Patch 6.01, I have been experiencing a rather frustrating error during play. I have attached the image showcasing the error, sometimes in Japanese and sometimes in English, without any explanation or code and just an option to click OK.





Would you please help explain this? It's becoming exceedingly challenging to play the game due to the added pressure of "waiting" to log in and being greeted by this error during play. It's borderline agonising...

Thanks in advance.
Please note that I mentioned in the subject that I play on iMac

Edit: Looks like it is related to the December 15 Date, all errors share the same date in both pictures even though they were taken 2 weeks apart (before 6.0.1 and after) and if it helps, the music keeps playing even after the error.