Hard constraint's both points there are at same position.
the ball is falling and after some frames of simulation hard constraint wants to handle the ball movement with respect to the happened constraint to ball offset at switch time.
how can i do this in a smooth way without any ball jumping and hard constraint length change at switch time?
Seems hard constraint considers just initial SOP level offset to the ball not simulated one, for its internal calculations which causes jumpy transition and after a couple of frames it ignores the ball's simulated offset completely.
Initial scene setup in the attachment.