After a G28 z-axis homing, there is a final z hop.
It was hoping to height z_hop as an absolute z height rather than relative.
If the z-axis home leaves the head at a z height higher than z_hop,
e.g. because you were using a probe to do z homing,
this meant that it was z hopping in the negative z direction, which
could result in crashing the toolhead.
Signed-off-by: Joshua Redstone <redstone@gmail.com>
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