Hi,
I use Real-Time online traffic, and when I was flying in Japan, I noticed that some callsigns were blank in the ATC, as you can see on this screenshot:
I check on FlightAware, and those flights were from Japan Airlines and All Nippon Airways, and their callsigns both contain spaces (Japan Air and All Nippon), so I think there could be an issue with the ATC being unable to read callsigns with spaces.
Could you please check this or confirm it is a known issue?
Thank you.