Same issue with 2 different H100i RGB Platinum pumps. I created a new thread not realizing it was such a hot topic here but I wanted to add to this main discussion.
I replaced quite a few parts in my PC thinking that it was a hardware issue or some incompatibility issue after I completed some upgrades. I was mainly using the Spiral Rainbow effect on the pump and fans.
I noticed numerous USB disconnects in many different situations (unplugging/plugging in hardware, installing software, opening programs etc.) however, one thing I did notice was when the issue starts (USB Disconnect, Light Flash, Fan RPM Increases etc), if I open the iCUE software, it isn't showing the fan or pump speeds increasing or decreasing and closing and restarting iCUE resets the issue.
Currently testing static lights to see if there is any change.
*Started using a customized static light theme for the pump and fans and have had zero issues. Installed a few programs, ran some programs that would cause issues previously and still stable.