Laggy collisions with default settings

Hello all!

I’m making a 3D game involving a CharacterController (capsule) interacting with a floor plane. In the game, when the character is not colliding with the plane, the game runs at a good 60FPS. However, when there is collision, it runs at 2-sih FPS. Does anyone know why this is happening? How do I fix it?

Here is my code, differing only from default on line 17:

extends CharacterBody3D

const SPEED = 5.0
const JUMP_VELOCITY = 4.5

# Get the gravity from the project settings to be synced with RigidBody nodes.
var gravity = ProjectSettings.get_setting("physics/3d/default_gravity")

func _physics_process(delta):
	# Add the gravity.
	if not is_on_floor():
		velocity.y -= gravity * delta

	# Handle jump.
	if Input.get_action_strength("jump") == 1 and is_on_floor():
		velocity.y = JUMP_VELOCITY

	# Get the input direction and handle the movement/deceleration.
	# As good practice, you should replace UI actions with custom gameplay actions.
	var input_dir = Input.get_vector("move_left", "move_right", "move_forward", "move_backward")
	var direction = (transform.basis * Vector3(input_dir.x, 0, input_dir.y)).normalized()
	if direction:
		velocity.x = direction.x * SPEED
		velocity.z = direction.z * SPEED
		velocity.x = move_toward(velocity.x, 0, SPEED)
		velocity.z = move_toward(velocity.z, 0, SPEED)


And my scene: