Physic issue with Joint since 2018.3

I'm having physic issue with the Joint system on unity 2018.3 (Was not happening on 2017.4)

Here is the usual behavior, it's a Configurable Joint (or a Spring joint)

But sometimes it get stuck out of nowhere, especially when it reach velocity 0.
Once it's stuck, the only way of having it to update, is to change any value within the editor (Even a boolean).

I've tried to run an Update with a random number changing values, but it doesn't "unstuck" the object.


Issue tested on 2018.3 b6, b7, b9, b10 and reproduced on Spring Joint, Configurable Joint and reproduced on different computers

(Case 1102075)

 

Anyone got a similar issue with Joints?

I can't really extract that into a specific testable build, as the repo is over 20gigs.
It's quite a big issue as it's breaking the game our side...

 

Could this be due to the new physics in unity ?

 

Ok So I found the issue, the rigidbody that was having the joint was set like that:

(it was perfectly functional in unity 2018.2)

But since unity 2018.3, it has to be in "Use gravity" or it randomly dont work

 

They're entirely different features... Kinematic is designed to never simulate... So it never should have worked previously at all.