I just met same issue. When the airplane I took almost arrived at U.S, I found android logo with erase data message automatically shown on my s9+ then the phone went into factory reset protection mode need wifi to verify but hotel wifi and other wifi can not pass verification with no reason. The phone just can not be used in my whole trip. After I backed from trip to home, I can only use home wifi to verify but factory reset was already done. This issue ruined whole trip. Still worry about next trip will automatically factory reset again.