Hi,
Reset the 18i20 to factory and set output to DAW, the PC is in high performance mode, all other sound (onboard etc) has been disabled, the PC is self built to high spec (for 2018), still getting pop's if I open more than one instance of a plugin such as ARP 2600 V3, disabled all other inputs for real hardware such as my Access Virus Ti2 and Roland Integra 7, its really annoying as I was considering the new OB-XA V plugin but not risking buying it at this time to get more pop's etc..