Swift + Physics: Wrong angle calculation on collision?

I have a simple SpriteKit App with walls and a ball. Both setup with a SKPhysicsBody.

When i apply a force in one direction, i expect the ball to reflect at the wall with the same angle when it collide but in opposite direction.

But sometimes i see the angle is weird.

I played a lot with all the physicsBody properties, but was not able to fix it. Sometimes the first reflections look good, but then the third or sixth and sometimes the first reflection is at wrong angle.

I read from different posts on other sites, people are kinda self-calculating the "correct direction". But i can't imagine SpriteKits physic engine is not capable to do so.

Check my attached image to understand what i mean. Can anybody help on this? I don't want to start playing around with Box2d for Swift, since this looks like it will be too hard for me to integrate into Swift.

Check the following image to understand my problem:

Link to image

This is the physicsWorld init on my GameScene.swift file where all my elements are added to:

self.physicsWorld.gravity = CGVectorMake(0, 0)

Adding all my code would be way too much, so i add the important pieces. Hope its enough for analyze. All elements like the ball, walls are SKSpriteNode's

This is the physicsBody code for the ball:

self.physicsBody = SKPhysicsBody(circleOfRadius: Constants.Config.playersize+self.node.lineWidth)
self.physicsBody?.restitution = 1
self.physicsBody?.friction = 0
self.physicsBody?.linearDamping = 1
self.physicsBody?.allowsRotation = false
self.physicsBody?.categoryBitMask = Constants.Config.PhysicsCategory.Player
self.physicsBody?.collisionBitMask = Constants.Config.PhysicsCategory.Wall | Constants.Config.PhysicsCategory.Enemy
self.physicsBody?.contactTestBitMask = Constants.Config.PhysicsCategory.Wall | Constants.Config.PhysicsCategory.Enemy

This is the physicsBody for the walls:

el = SKSpriteNode(color: UIColor.blueColor(), size: CGSize(width: Constants.Config.wallsize, height: Constants.Config.wallsize))
el.physicsBody = SKPhysicsBody(rectangleOfSize: CGSize(width: Constants.Config.wallsize, height: Constants.Config.wallsize))
el.physicsBody?.dynamic = false
el.physicsBody?.categoryBitMask = Constants.Config.PhysicsCategory.Wall
el.physicsBody?.collisionBitMask = Constants.Config.PhysicsCategory.Player
el.physicsBody?.contactTestBitMask = Constants.Config.PhysicsCategory.Player

At the end i just call the applyImpulse function on the balls physicsBody to make it moving in the physics simulation.

Also check my attached second image/gif. It shows the edge collision problem with a simple skphysics app without any special parameterization. just a rectangle with a ball in it and one vector applied as impulse.

Link to this gif

Please help, i can' imagine this is a bug in SpriteKit Physics nobody is aware off. What am i doing wrong? I need perfect angle calculation without any friction or damping, the ball should reflect at any wall (not only horizon. and vertical, but also diagonal or circles)