Sankey is not updated on callback

Python 3.8.5; Plotly 4.14.1; Dash 1.19.0

Plotly’s Sankey is not updated with new data on callbacks. A Sunburst plot based on the same data works correctly, as you can see in this example.

value data are changed and passed to JS correctly:

import plotly.graph_objs as go

import dash
import dash_html_components as html
import dash_core_components as dcc
from dash.dependencies import Output, Input
import random

app = dash.Dash(__name__)
app.layout = html.Div(
    [
        html.Button('Change values',
                    id='btn_change',
                    n_clicks=0),
        
        dcc.Graph(
            id="fig_sunburst",
            figure=go.Figure(),
            animate=True,
        ),
        dcc.Graph(
            id="fig_sankey",
            figure=go.Figure(),
            animate=True,
        ),

        dcc.Interval(
            id=f"update",
            interval=2000,
            n_intervals=0
        ),
    ],
)

@app.callback(
    Output('fig_sunburst', 'figure'),
    Output('fig_sankey', 'figure'),
    Input('btn_change', 'n_clicks')
)
def traces_update(n_clicks):
    print(f"update {n_clicks}")
    
    # random data
    a1 = random.randint(10, 100)
    a2 = random.randint(10, 100)
    a3 = random.randint(10 ,100)
    a0 = a1+a2+a3
    
    b1 = random.randint(10, 100)
    b2 = random.randint(10, 100)
    b0 = b1+b2
    
    tot = a0+b0
    
    fig_sunburst = go.Figure(
        go.Sunburst(
            ids=['tot', 'a0', 'a1', 'a2', 'a3', 'b0', 'b1', 'b2'],
            labels=['tot', 'a0', 'a1', 'a2', 'a3', 'b0', 'b1', 'b2'],
            parents=['', 'tot', 'a0', 'a0', 'a0', 'tot', 'b0', 'b0'],
            values=[tot, a0, a1, a2, a3, b0, b1, b2],
            branchvalues="total",
            insidetextorientation='horizontal',
        )
    )
    fig_sunburst.update_layout(go.Layout(width=400, height=400,
                                 margin=dict(t=20, l=20, r=20, b=20),))
        
    fig_sankey = go.Figure(
        go.Sankey(
            node=dict(
                label=['tot', 'a0', 'a1', 'a2', 'a3', 'b0', 'b1', 'b2'],
            ),
            link=dict(
                source=[0, 0, 1, 1, 1, 5, 5],
                target=[1, 5, 2, 3, 4, 6, 7],
                value=[a0, b0, a1, a2, a3, b1, b2],
            ),
        )
    )

    fig_sankey.update_layout(go.Layout(width=400, height=400,
                                 margin=dict(t=20, l=20, r=20, b=20),))
    
    print(fig_sankey["data"][0]["link"]["value"])
    
    return fig_sunburst, fig_sankey

app.run_server()

Start by running the supplied Python Dash callback example with the stated Python, Plotly, and Dash versions, and compare the Sankey and Sunburst updates after clicking “Change values.” Trace the callback-to-graph update path for Sankey data; done means the Sankey link values visibly refresh on callbacks just as the Sunburst does.