Problem in rig tool a curved object

Hi. Take a look at attached image. I have a single octopus hand. I added a curve/bone rigging tool in two situations:
1- When I draw a bended hand and then use rigging tool in bone/curve mode on it and then try to have a straight hand in upcoming/next frames, it shows some malfunctions and some extra lines appears.

2-When I draw a straight hand and try to animate it in next frames and try to bend the hand it is ok (straight to bend is ok. Adding rigging/deformers in straight is ok).

Question: how could I have an elegant curve/bone rigging tool or having a nice deformer on a bended hand and then animate it without distortion and extra line? Is there any options in rigging tool I need to manipulate?