Two issues with MX Master 3:
Left click sometimes generates a 'bounce' feeling and sound, like a ruler being flipped on a table edge or a ball bouncing, or like it's slightly stuck and reverting to normal position it bounces. Feels like it's related to the magnets.
Second issue is that switching between windows using the keyboard, I can feel the change in the scroll wheel, it clicks and shifts between one window and the next (can be different windows of the same application, e.g. Excel, or different editors).