During my last flight with Real Live traffic ON, the ATC was communicating with a plane with the callsign “Waypoint 154”. This plane was heading to EBBR. The plane responded also with callsign “Waypoint 154”. The callsign was continuously “wrong” until that Real Live Traffic plane was landed at EBBR. Till now this happened to me only after the update to 1.15.7.0.
EDIT: Probably it was because I used the ATC European Phraseology 1.4. MOD. I did some more tests and switched to the standard ATC file. Several hours of observing ATC traffic at EDDF seems everything is normal now.