Why is clamp being ignored after enough mouse motion?

Lethn I took your code and simplified it to just the mouse look component and I could not get it to print anything out of the range of -.75 to .75 regardless of how fast i moved my mouse:

extends CharacterBody3D

var mouseSensitivity = 0.2
var direction = Vector3()
var gravityVector = Vector3()
var horizontalVelocity = Vector3()
var movement = Vector3()
var customVelocity = Vector3()
var fall = Vector3()
var speed
var defaultMoveSpeed = 5.0
var sprintMoveSpeed = 10.0
var crouchMoveSpeed = 1.0
var gravity = 10
var jumpHeight = 6
var horizontalAcceleration = 6

var swayAmount = 30
var verticalSwayAmount = 30

var plasmaPistolMaxGunShake = 1.5
var crouchingPlasmaPistolMaxGunShake = 0.5

@onready var mouseLookNode = $MouseLookNode
@onready var playerCollisionShape = $PlayerCollisionShape
@onready var playerCamera = $MouseLookNode/PlayerCamera




var isHittingCeiling = false
var isCrouching = false
var isSprinting = false
var isPlayerFiring = false
var isFlashlightEnabled = false

var canEnterDriverSeat = false
var vehicleDriverArea

func _ready():
	Input.set_mouse_mode(Input.MOUSE_MODE_CAPTURED)
	playerCamera.make_current()
	isCrouching = false
	playerCollisionShape.set_deferred(("disabled"), false)
	speed = defaultMoveSpeed
	

func _unhandled_input(event):
	if event is InputEventMouseMotion:
		rotate_y(deg_to_rad(-event.relative.x * mouseSensitivity))
		
		mouseLookNode.rotate_x(deg_to_rad(mouseSensitivity * event.relative.y))
		mouseLookNode.rotation.x = clamp (mouseLookNode.rotation.x, -(PI/4), PI/4)
		prints(mouseLookNode.rotation.x);
#		mouseLookNode.rotation.x = clamp(mouseLookNode.rotation.x, deg_to_rad(-80), deg_to_rad(80))

```		

It might be easier if you could upload a zip of the project somewhere (or send it to one of us if you don't want it public yet) so we can see it happening live and debug it. I tried some of the code above (in Godot 3.5 and 4) and couldn't get it to fail. It seems like something elsewhere is affecting it after each clamp.

Lethn I can assure that I have no interest in anything other than making tiny gremlins walk around procedural terrain populated with crappy tree models, and I only have a middling interest in that.

If you want my opinion, you have something else going on in your code. Code does what you tell it to, and i've never seen an instance where it decided to do something else. It's pretty unlikely that the clamp is your problem.

In a pinch you can put some if(....x > abs(80degrees)) prints() messages in different places to debug this, or just put a breakpoint inside of that same if. You'll probably find that it is being affected somewhere else.

Lethn Is there any chance at all you're colliding with something? The point of my video was to show that collisions themselves can affect the Y access of the parent object and screw up the total rotation of the player (of which your camera is attached to). I don't know why shaking the camera like that would do that though.

There's a lot of oddities that can happen with rotations.
I've seen some engines (or just euler angle classes) that when the pitch goes above 90 or below -90 it flips the entire system. So if you set it to 100 degrees pitched up, it would actually turn into 80 degrees up, 180 yaw (face backwards) and 180 roll (flip upside down). That meant you couldn't clamp a value to 90, because it never stored the larger value. In particular that can happen if the engine only gives you quaternions and you manually turn them back into angles.

Gimbal lock is always so fun to debug, isn't it... /s

I know it's pretty old topic, but me and my friend trying one of Lukky's Godot tutorials, from youtube. And he did camera rotation for 3rd person view, but without any rotation limit. I googled and found how to that with clamp, but quickly noticed that rotation become broken if I move mouse too fast vertically. Camera leans a bit, and Mathf.clamp stop working. I displayed rotations on a label, and noticed that Y axis changes after quick movements of mouse.
I noticed that this happens only when I do:

        Vector3 camera_rot = camMount.Rotation;
        camera_rot.X = Mathf.Clamp(camMount.Rotation.X, Mathf.DegToRad(-70), Mathf.DegToRad(70));
        camMount.Rotation = camera_rot;

So it's became broken, after I copy rotation to temp Vector3, change it, and then return values back to Rotation property.
It's my first game engine that I try, and I barely coded anything complicated, before, or what's required actual math, so I'm really was confused why this happening. And I'm still confused.

I was able to kinda fix it, by adding
camera_rot.Y = Mathf.Pi;
after clamp.
Now reading this, I see that issue happens because -180deg rotation, and in that tutorial Player base node was rotated 180 Y (and, I guess, I rotated it to -180) , because coordinate system in Godot is different to that from Mixamo or something like that, I'm still not sure.
So I've reset Player rotation to 0,0,0 from -180, and rotated camera to +180.
And now it's not breaking even with craziest mouse moves.
I really wish I able to understand what exactly goes wrong, but even after reading this thread I'm still not sure.

Lethn it's not hardware cause I'm having the exact same problem. have you fixed it yet? if so please tell me how!