Plotly express add_trace() exhibits unexpected behavior if number of rows is greater than 1000

[r-beginners]

I have run your code and verified the contents. When the number of data exceeds 1000 in a scatterplot, it changes to scattergl, which is a scatterplot for large amounts of data, instead of the normal scatter, see here for more information about scattergl. My guess is that is the cause. If you rewrite each chart in a graph object, the overlap is the same even if the number of data is 1001.

import plotly.graph_objects as go
import numpy as np
import pandas as pd

n_row = 1001
df_1 = pd.DataFrame({'x': np.random.rand(n_row), 'y': np.random.rand(n_row)})
df_2 = pd.DataFrame({'x': np.random.rand(20), 'y': np.random.rand(20)})

fig = go.Figure()

fig.add_trace(go.Scatter(
    x=df_1.x,
    y=df_1.y,
    mode='markers',
    marker=dict(color='red', size=4)
))

fig.add_trace(go.Scatter(
    x=df_2.x,
    y=df_2.y,
    mode='markers',
    marker=dict(color='Blue', size=20)
))   

fig.show()