Strange selector alignment behaviour

[khenderick]

Since a few weeks my MMU2s selector behaves strange when it's supposed to align itself. I can't link a certain action such as firmware upgrade or changed setting to have started this changed behaviour.

Expected: After the MMU2s boots and when the right button is used to navigate the selector to a given input, it will first home the selector by moving to the right, bump a few times (just like e.g. the bed does when you start a print), and then move to the correct location.

Observed: After the MMU2s boots and when the right button is used to navigate the selector to a given input, the selector moves a few times briefly to the right, incorrectly thinking it has reached the right end, and then moves too much to the left.

I cannot feel any jamming. When the printer is turned off I can without any issues manually rotate the motor axis moving the selector to any position. When the observed behaviour completes (after skipping tons of steps driving the selector against the left wall), I can perfectly use the buttons to navigate to any of the 5 positions.

I filmed the issue: https://www.youtube.com/watch?v=wYMSInwk2CI

[workinghard]

One of my MMU boards is showing same behaviour. Swapping to a new one (same model/revision) solved the issue. I think it's a hardware board issue.