It seems confirmed from different people. Have you also Zendesk this?
NB: to me, it looks like the simulator is sending wrong string data to the ATC window. I’ve seen similar issue in MP lately where the displayed player name had a numeral suffix, like #248
Given I’ve seen other reports where it looked like displaying similarly built numbers, I’d relate this to a bug where the simulator is sending a pointer to some memory instead of a pointer to the actual string chars (in C++).