I have tried to find this problem, and if I found something near it the resolve wouldn't work. I have had this audio interface for around a year and randomly this crackling noise started. I am new to audio interfaces so I might be doing something wrong. I cant seem to get it to go away even when I changed the block size, sample rate and kHz. I plugged it into all 2.0, 3.0 and 3.1 USBs and all of them give them same result. I have a AT-2035 and a keyboard plugged into it and occasionally a guitar. I am using Voicemod right now to try to silence the crackles as much as possible.
YouTube link to problem-
PC specs
CPU- i7-7700k
GPU-GTX 1080 SC
RAM- 16GB DDR4