Path animating incorrectly with SampledPositionProperty

Hi, I am using SampledPositionProperty to create an animated path from tracking (GPS) data and using cesium 1.114 within a vue.js based application.

First, I tested with the czml sandcastle example of drone flight and experienced the same behaviour with the path not animating correctly.

var pathEntity = entities.add({
        availability: new Cesium.TimeIntervalCollection([ new Cesium.TimeInterval({ start: startTime, stop: stopTime }) ]),
        position: positionProperty,
            width: 2,
            resolution : 1,
            leadTime: 5,
            trailTime: 50,        
            color: Cesium.Color.RED,
        point: { pixelSize: 15, color: Cesium.Color.YELLOW },

Seems simple code but the behaviour is not as expected. The point (yellow dot) animated correctly, and the blue polyline draws correctly, just the path in animation (dragging/playing) is incorrect.

Any help is appreciated, thanks.

Ceisumjs path