Help Relax the rope when required

[Romahaaa]

Posting the solution here based on our email chat with the developer. Just in case if someone will have similar issue

Me

Trying to reproduce the same issue, it seems I found the parameter which causes the rope jittering on attach - it's Physics > Sleep Threshold. It was set to 0.001 while Unity default value is 0.005. 
Changing that in the Unity project I sent, you may notice the issue I described. 

I am not 100% sure I can change it back to default 0.005 (most likely there was a reason for that). Would be good to figure out and close that question - is it expected behaviour or not. 

Jose (or other developer) answer

Sleep threshold determines the kinetic energy level below which rigidbodies are considered static. Bodies that stay below this threshold for a while are assumed to not be moving anymore so they're put to "sleep" -skipped by the simulation-  to save resources, until they wake up due to external forces being applied to them.

If your sleep threshold is too low it might cause objects to never go to sleep, or constantly alternate between sleep/awake. If it's too high, bodies will fall asleep and stop moving even when they should not. Under normal circumstances, the default value is good and should not cause problems. 
 
An excessively low sleep threshold might be causing the rigidbody that's hanging from the rope to briefly enter the asleep state. As you move the top of the rope, it gets slightly stretched since the rigidbody is asleep and unable to move. Once it wakes up due to the rope attempting to modify its velocity and becomes able to move again, you get the slingshot-like behavior in your original post.