Question about crackling noise and AT5

[obispojoe]

For whatever reason at some point after upgrading to some version of AT 5.10.x, I started to get crackling noises when playing guitar through an iRig HD interface into a MacPro 2013 which is pretty much maxed out (12 core Xeon, 128 GB RAM, etc.). The usual advice is to increase the buffer size but this made things worse - the higher the buffer size the worse the crackling even to the point where no sound was produced. So unintuitively I decreased the buffer size from 256 to 128 and that seemed to solve the problem. Can someone explain why that solved the problem as lowering the buffer size would put more strain on the system? Just curious.