[Bullet] RigidBody2D bounces when passing on top of two perfectly aligned StaticBody2Ds

[nosklo]

Godot version:
Happens on 3.1 stable and 3.1.1rc1

OS/device including version:
ubuntu 18.04 / nvidia GTX1070 8GB driver 418.56

Issue description:
When creating two StaticBody2Ds, no matter how well aligned they are, a RigidBody2D passing over them will jump upwards sometimes. I expected the RigidBody2D to just roll over the connection since there is no gap at all, but it jumps instead.

GIF video of the issue
https://media.giphy.com/media/d7SgPewvXmuwsfw8w9/giphy.gif

Steps to reproduce:

Attach the GDScript code below to a Node2D in a new project, and run:

extends Node2D

const STATIC_SIZE = 2000
onready var img = preload('res://icon.png')

func _ready():
	var rb := RigidBody2D.new()
	
	var s = Sprite.new()
	s.texture = img

	rb.add_child(s)

	# Add a circle shaped collision
	var rb_col := CollisionShape2D.new()
	rb_col.shape = CircleShape2D.new()
	rb_col.shape.radius = 50
	rb.add_child(rb_col)

	# Configure to have no friction and no damp
	rb.linear_damp = 0
	rb.physics_material_override = PhysicsMaterial.new()
	rb.physics_material_override.friction = 0
	
	# apply impulse
	rb.apply_impulse(Vector2.ZERO, Vector2(1050, 0))

	# follow with a camera
	var camera := Camera2D.new()
	camera.current = true
	rb.add_child(camera)

	add_child(rb)
	
	# create 10 consecutive StaticBody2D perfectly aligned
	var pos := Vector2(STATIC_SIZE / 2, 200)
	for x in range(0, 10):
		var ground := StaticBody2D.new()
		var ground_col := CollisionShape2D.new()
		ground_col.shape = RectangleShape2D.new()
		ground_col.shape.extents = Vector2(STATIC_SIZE / 2, 100)
		ground.add_child(ground_col)

		# Add a sprite so we can see where the division is
		s = Sprite.new()
		s.position = Vector2(-STATIC_SIZE/2, -50)
		s.texture = img
		ground.add_child(s)
	
		ground.position = pos
		add_child(ground)

		pos.x += STATIC_SIZE

[T0BiD]

Happens for 3d as well

[akien-mga]

Fixed by #56801.