I have an issue with a turret mesh sink into the floor when i hit play.
I did try with mesh collision ( convex on/off ), did try box collision.
Start position.
Position after i click play ( the turret sink a bit into the ground ).
I did try plane, box objects as the ground,
All give same results.
I did try with new scene (No scripts), just the turret with rigidbody on a simple plane, it sink into the plane.
I had to use box collider with size bigger the the turret on the Y axes just to have the turret stay above ground.
This problem happend also with a sphere, it sink a bit into the ground ( plane ).
Don’t know what’s the size of the turret is. In the case that it is quite small, like 0.1 units, you may think about either increasing it, or lowering the Min Penetration For Penalty value.