Static bodies still moving - sprite-kit

Question

this may be a duplicate of
Static Physics body still moving with contact
but I have not the reputation to add a comment.
My problem is with collisions and static bodies. I'm working on a little game and I have a player, so configured (from sks file):
player = worldNode.childNodeWithName("player") as! SKSpriteNode
let playerBodyTexture = SKTexture(imageNamed: "player_physicBody_mask")
player.physicsBody = SKPhysicsBody(texture: playerBodyTexture, size: CGSizeMake(player.size.width, player.size.height))
player.physicsBody!.usesPreciseCollisionDetection = true
player.physicsBody!.categoryBitMask = PhysicsCategory.player
player.physicsBody!.collisionBitMask = PhysicsCategory.ground | PhysicsCategory.enemies
player.physicsBody!.contactTestBitMask = PhysicsCategory.enemies
player.physicsBody!.restitution = 0
player.physicsBody!.friction = 0
player.physicsBody!.allowsRotation = false}
an enemy:
worldNode.enumerateChildNodesWithName("enemy") { node, _ in
let enemy = node as! SKSpriteNode
enemy.name = "enemy"
enemy.physicsBody = SKPhysicsBody(circleOfRadius: 17)
enemy.physicsBody!.dynamic = true
enemy.physicsBody!.mass = 0.4
enemy.physicsBody!.restitution = 0
enemy.physicsBody!.categoryBitMask = PhysicsCategory.enemies
enemy.physicsBody!.collisionBitMask = PhysicsCategory.ground | PhysicsCategory.player
enemy.physicsBody!.contactTestBitMask = PhysicsCategory.player}
and I have the platfrom brick, so configured:
worldNode.enumerateChildNodesWithName("fixedBlock") { node, _ in
let fixedBlock = node as! SKSpriteNode
fixedBlock.name = "fixedBlock"
let fixedBlockBodyTexture = SKTexture(imageNamed: "tripleBlocks_physicBody_mask")
fixedBlock.physicsBody = SKPhysicsBody(texture: fixedBlockBodyTexture, size: CGSizeMake(fixedBlock.size.width, fixedBlock.size.height))
fixedBlock.physicsBody!.categoryBitMask = PhysicsCategory.ground
fixedBlock.physicsBody!.collisionBitMask = PhysicsCategory.player | PhysicsCategory.enemies
fixedBlock.physicsBody!.contactTestBitMask = 0
fixedBlock.physicsBody!.dynamic = false
fixedBlock.physicsBody!.affectedByGravity = false
fixedBlock.physicsBody!.allowsRotation = false
fixedBlock.physicsBody!.pinned = false
fixedBlock.physicsBody!.friction = 0.3
fixedBlock.physicsBody!.restitution = 0}
When the player jumps on the enemies, he has an impulse (like Super Mario :-)), so I have this:
func didBeginContact(contact: SKPhysicsContact) {
let collision: UInt32 = contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask
if collision == PhysicsCategory.player | PhysicsCategory.enemies {
self.player.physicsBody!.applyImpulse(CGVectorMake(0, 500))}}
Ok... sometimes, often, when the player jumps on enemy, the impulse appens correctly, but the ground tile moves down, also if its dynamic propriety is set on false. I tried to apply a JointFixed on the ground tile but when it is pushed down, its physic body "glitch"; I tried to print the physicsBody velocity propierty of the ground tile and when the problem occours, the velocity's dx vector is >100, but should static bodies not be affected by forces?
Any idea?
Many thanks