I have used two X1 safety capacitors in series with an isolator (ISOW7842DWE). I have fault on EMC test on 64MHz. When I remove the capacitors, the EMC issue is reduced by 6dB.
I have used two safety capacitors to obtain 8kV spike protection. I do not know why there are more radiated emissions on the board when I use the safety capacitors with the isolator.