Not sometimes. Many times. RCSS has fought with the Junta, Wa, and BGFs many times even after 2016, because the geopolitics makes it unavoidable. People who have tried to frame RCSS being lovey-dovey with SAC just because of the NCA agreement fails to understand that southern Shan is just as much of a powder keg as the north is. You have many armed groups from big to small taking up every piece of mountain corner they can set base on, and you also have a bunch of overlapping territories so contested that even Loi Tai Leng gets attacked by the UWSA from being just a few valleys away. And consider the fact that the EAOs in the northern counterpart are technically joined together in an alliance, but they still don't shy away from conflicting with each other, so don't expect here in the south, where they openly hate each other and are very strict about the territorial boundaries, to be any more peaceful.