Dash app hangs sometimes with juliacall

Dash Python
1

I am trying to create a dashboard part of which runs some Julia code via juliacall. I have found that when the Julia code errors or prints then the Dash app hangs indefinitely. Is there a way around this?

A minimal example:

from dash import Dash, html, callback, Output, Input
import juliacall

app = Dash()

app.layout = html.Div(
    children=[
        html.Div(
            id="box",
            style={"background-color": "blue", "width": "500px", "height": "500px"},
        ),
        html.Div(
            html.Button(
                id="button", n_clicks=0, style={"width": "100px", "height": "50px"}
            ),
        ),
    ],
    style={"display": "flex"},
)


@callback(
    Output("box", "style"),
    Input("button", "n_clicks"),
    prevent_initial_call=True,
)
def update_div(nclicks):
    bc = "blue" if nclicks % 2 == 0 else "green"
    if nclicks == 2:
        juliacall.Main.seval('println("hi from julia")')

    return {"background-color": bc, "width": "500px", "height": "500px"}


if __name__ == "__main__":
    app.run(debug=True)