Binding : What do I miss?

[balage1551]

I use (sometimes complex) bindings with no problem, but stucked with this one.
I have this code (simplified):

    val deltaXProperty = SimpleDoubleProperty(100.0)
    val deltaYProperty = SimpleDoubleProperty(100.0)
    
    
    class TranslateInfo(x: Double = 0.0, y: Double = 0.0) {
        val xProperty = SimpleDoubleProperty(x)
        var x by xProperty
        val yProperty = SimpleDoubleProperty(y)
        var y by yProperty
    
        val translateXProperty = ReadOnlyDoubleWrapper(0.0).apply {
            bind(xProperty.add(deltaXProperty))
        }
        val translateYProperty = ReadOnlyDoubleWrapper(0.0).apply {
            bind(yProperty.doubleBinding(deltaYProperty) { y + deltaYProperty.value } )
        }
    
        override fun toString(): String {
            return "FloorTranslateInfo[x= $x, y=$y, tx=${translateXProperty.value}, ty=${translateYProperty.value}}]"
        }
    }
    
    
    fun main() {
        val t = TranslateInfo(10.0,20.0)
        println("Initial: $t")
        t.x = 30.0
        println("Change x: $t")
        t.y = 40.0
        println("Change y: $t")
    }

The first type of binding I use in translateX works fine and the value is updated. However, using the doubleBinding function doesn't binds the values and the bound value isn't updated.
The output:

Initial: FloorTranslateInfo[x= 10.0, y=20.0, tx=110.0, ty=120.0}]
Change x: FloorTranslateInfo[x= 30.0, y=20.0, tx=130.0, ty=120.0}]
Change y: FloorTranslateInfo[x= 30.0, y=40.0, tx=130.0, ty=120.0}]

It should be some simple mistake I doesn't see, but can't make it work. (I could use the first syntax, but z (which I left out) has a more complex expression with four or five dependencies.