How to remove thumbnails of events?

Hello,
I can not delete the image of an event by the administration (delete the current thumbnail and save).
Even by checking the checkbox and without choosing a new thumb, it does not erase the current thumb.

How can I do?

Thanks in advance.

Kind regards.

That's strange. If you check on the checkbox, the thumbnail should be deleted. Could you submit a support ticket so that we can check the issue directly on your site?

Regards,

Tuan