Upgraded Project to 2019.1 from 2018.1 causing problem

Hi Everyone,

I have upgraded my project to 2019.1 from 2018.1 and it's behaving very strangely.

I have a marry-go-round with rigid body and constraint (X, Y, Z in position and X, Z in rotation) and that marry-go-round is a fixed joint with another rigid body and that rigid body is moving marry go round using "AddRelativeForce" with "ForceMode.VelocityChange" and at some point, when velocity will increase too much, I broke that fixed joint and let merry-go-round rotate smoothly for some seconds and it gradually stops moving.

But in Unity 2018.1 merry-go-round stops like usual and rotates at Y angel only, but after I upgraded my project to 2019, it rotates at X-axis also, so in constraints, I tried to set it again from the inspector but no result, so I remove the constraints from inspector and set it using script (in Awake), but after setting it from scripts it behaves very strangely. Now, my merry-go-round will increases the speed at a very fast pace, I mean before I broke the Fixed Joint, it rotates at a very fast pace. I remove the constraints from code and set it again using the inspector. But still, the problem is not solved. I think I missed something because of change in PhysX engine.

Let me know if you guys understand my concern and it's great if anyone can suggest something which I can try to solve.