`busy_indicator` always busy

Dear Panel developers,
after upgrading Panel from 0.14 to 1.x the global busy_indicator of the template(s) is constantly rotating.

The problem is still present in panel 1.2.1

$ mamba list | grep panel
panel                     1.2.1              pyhd8ed1ab_0    conda-forge

A minimum working example to reproduce this bug is given below.
Is there a configuration setting to tweak until this bug is fixed?

Best regards,

import panel as pn

if __name__ == "__main__":
    test = pn.pane.Markdown("I am a test")
    tmpl = pn.template.VanillaTemplate(main=test).servable()