Stack underflow on yielding

[xoSauce]

Godot version:
3.2.1
OS/device including version:
Windows 10
Issue description:
Stack underflow on yielding
Throws error:
E 0:00:12.232 _disconnect: Disconnecting nonexistent signal 'checkpoint_reached', slot: 1305:_signal_callback. <C++ Error> Condition "!s->slot_map.has(target)" is true. <C++ Source> core/object.cpp:1522 @ _disconnect()

I am unsure whether this error occurs because of the stack underflow or causes the stack underflow.

Steps to reproduce:
Running the following script attached to a node:

extends Spatial

export (Array) var checkpointPaths
export var moveSpeed := 100
onready var tween : Tween = $Tween
onready var rotate : Tween = $Rotate

signal checkpoint_reached
var moveToObjective = null

func _ready():
	print("Ready:", checkpointPaths)
	moveToObjective = move_to_objective()

func move_to_objective():
	var nav = get_node("../")
	for checkpointPath in checkpointPaths:
		var checkpointObject = get_node(checkpointPath)
		var navPoint = nav.get_closest_point(checkpointObject.translation)
		var path = Array(nav.get_simple_path(transform.origin, navPoint, true))
		follow_current_path(path)
		yield(self, "checkpoint_reached")
		print("Here")
		
func lookAtTarget(target):
	if (target != transform.origin):
		look_at(target, Vector3.UP)
		self.rotate_object_local(Vector3.UP, PI);
	
func follow_current_path(path) -> void:
	for p in path:
		p.y = 0
		print("Going to:", p)
		var duration = translation.distance_to(p) / (moveSpeed * get_physics_process_delta_time())
		lookAtTarget(p)
		tween.interpolate_property(self, 'translation', translation, p, duration, Tween.TRANS_LINEAR, Tween.EASE_IN)
		tween.start()
		yield(tween, "tween_completed")
	emit_signal("checkpoint_reached")

Minimal reproduction project:
3DTowerDefense.zip

[Calinou]

(unsure how to attach it as I don't see any option to upload zip archive. I can upload to dropbox/google drive if required)

Drag and drop a ZIP archive smaller than 20 MB to the comment window while you're editing the comment.

[KoBeWi]

(unsure how to attach it as I don't see any option to upload zip archive. I can upload to dropbox/google drive if required)

[Calinou]

@xoSauce Bump 🙂 Could you upload a minimal reproduction project, please?

[xoSauce]

3DTowerDefense.zip

That should hopefully do it!
Apologies for the delay on this. The GitHub email got sent to spam (figures ...).

I notice the stack underflow when it turns towards the 2nd checkpoint.

[KoBeWi]

I don't get the stack underflow error, but there are errors about nonexistent signal and instance gone, both invalid.

I wonder if it has something to do with yields inside for loops.