Time for a bit change! The PCB housing the switches for left and right clicks comes off with four P0 screws and another ZIF connector.

The scroll wheel assembly is held in with two P0 screws at the front. There's also a connector for the motor hiding under the ribbon cable for the PCB you just removed.

These screws aren't visible in this step, but can be seen in the previous one. I'm terrible at taking pictures.

You can see some of the debris causing my scrolling issues in the last photo.