Weird G29 behavior

When performing the procedure my arm drops, then the Z descends and then moves back up before moving down again to probe the bed. The weird part is that I thought that is was supposed to move down and when the probe touches go back up and then descent again at a lower rate for accuracy. On my printer the probe never touches the bed before it moves back up. The slower decent does probe the bed.

Is this normal?

What happens if you manually trigger the switch before it moves very far? Does it recognize the switch got pressed?

I had a similar issue, it ended up being the wiring to the switch was getting pulled while extending the arm. Marlin thought it was triggered so it never touched the glass.