This has been happening to me ever since I switched to the new wc3 launcher that allows you to switch between RoC/TFT in one client. I have reinstalled over 20 times from official download links and it keeps happening. When I log onto the RoC client, it IS the RoC client. it shows the green RoC fog/rain background, but shows a TFT icon next to my name, says there are over 5,000 people currently on TFT, and when I go to play a ladder game, there are only TFT maps, and it matches me with someone on TFT and then the game desyncs at start because technically I’m on RoC and TFT simultaneously.
Whenever I log onto RoC, the server thinks I am on TFT. I have a TFT icon, TFT ladder maps but I'm on the RoC client. And if I play a random ladder game, it desyncs instantly and someone gets a loss. So it's basically an unintentional, volatile drop hack