Application cusomizer - Footer disappears on modern event page refresh

I have developed a simple application customizer(extension) which adds a div section in footer placeholder only in a modern SharePoint event page. The footer is not required any where else in the site but required only on event detail page. 

When I install the application extension and activate the feature the footer appears but on subsequent page refreshes or post backs the footer disappears. it never comes back and once I deactivate and activate the feature the footer again appears and then it vanishes.

On activating the feature:

On page refresh :

it it prohibited to add application customizers to modern event page?

Regards

Gnyanendra Ray