drag grouped elements move not continuous - d3.js

Question

I try move a grouped element but after click and drag, the elements jumped away.
demo()
function demo() {
var tooltip = d3.select('body')
.append('div')
.attr('id','tooltip')
.style('position','absolute')
.style('opacity',0)
.style('background','lightsteelblue')
var svg = d3.select("body")
.append("svg")
.attr("width", 300)
.attr("height", 200)
.style("background", "#ececec")
add_grid(svg);
var data = [
{
text: "O",
x: 50,
y: 50
},
];
var g = svg.append('g')
var fontsize = 20;
var box = g.selectAll(".box")
.data(data)
.join('g')
.attr('class','box')
.attr("pointer-events", "all")
box.call(
d3.drag()
.on("start",function(event,d) {
d3.select(this).raise().classed("active", true);
d3.select('#tooltip')
.transition().duration(100)
.style('opacity', 1)
})
.on("drag",function(event,d) {
d.x = event.x
d.y = event.y
d3.select(this).attr('transform',`translate(${d.x},${d.y})`)
var desc = "(" + d.x.toFixed(1) +"," + d.y.toFixed(1) + ")"
d3.select('#tooltip')
.style('left', (event.x+2) + 'px')
.style('top', (event.y-2) + 'px')
.text(desc)
})
.on("end", function dragEnd(event,d) {
d3.select(this).classed("active", false);
d3.select('#tooltip').style('opacity', 0)}
))
.on('mouseover', function(event,d) {
})
.on('mouseout', function(event,d) {
})
.on('mousemove', function(event,d) {
})
.on("mousedown", function(){
})
.on("mouseup", function(){
});
var txt = box.append("text")
.attr("text-anchor", "middle")
.attr("dominant-baseline",'text-before-edge')//'central')//text-bottom
.attr("font-size", fontsize)
.attr("x", (d) => d.x)
.attr("y", (d) => d.y)
var tspan = txt.selectAll(".tspan")
.data((d) => d.text.split("\n"))
.join("tspan")
.attr("class", "tspan")
.attr("x", function (d) {
let x = +d3.select(this.parentNode).attr("x");
return x;
})
.attr("y", function (d,i) {
let y = +d3.select(this.parentNode).attr("y");
return y + i*fontsize * .9;
})
.text((d) => d);
box.each((d,i,n) => {
var bbox = d3.select(n[i]).node().getBBox()
var padding = 2
bbox.x -= padding
bbox.y -= padding
bbox.width += 2*padding
bbox.height += 2*padding
d.bbox = bbox
})
.attr('transform',d => `translate(${0},${-d.bbox.height/2})`)
.append('rect')
.attr('x',d => d.bbox.x)
.attr('y',d => d.bbox.y)
.attr('width', d => d.bbox.width)
.attr('height',d => d.bbox.height)
.attr('stroke','red')
.attr('fill','none')
add_dots(svg,data)
function add_dots(svg,data) {
svg.selectAll('.dots')
.data(data)
.join('circle')
.attr('class','dots')
.attr('r',2)
.attr('cx',d => d.x)
.attr('cy',d => d.y)
.attr('fill','red')
}
function add_grid(svg) {
var w = +svg.attr("width");
var step = 10;
var mygrid = function (d) {
return `M 0,${d} l ${w},0 M ${d},0 l 0,${w}`;
};
var grid = [];
for (var i = 0; i < w; i += step) {
grid.push(i);
}
svg
.append("g")
.selectAll(null)
.data(grid)
.enter()
.append("path")
.attr("d", (d) => mygrid(d))
.attr("fill", "none")
.attr("stroke", "green")
.attr("stroke-width", 0.5);
}
}
<script src="https://unpkg.com/d3#7.0.4/dist/d3.min.js"></script>