Chosen Solution

Roomba 960 making noise after side brush replacement.

Take it out and follow the guide on replacing it. Look for any broken parts: iRobot Roomba 960 Side-Brush Replacement

Roomba 960 side brush was making a click click noise. Motor working fine. I took the brush off and a little WD-40 sprayed inside and brush put back on. Solution was a simple fix and wanted to share in case it helps.