Duplicate Email received by admin

Hello,

I am encountering the following issue

By and then, admin get twice the same appointment notification email (with same ID)

I also noticed that when I click and decline appointment, just after that I receive again the email as is the user had scheduled a new appointment even though infos are the same…

I plugins are up to date. For emails, I am using Mailjet for WordPress
Any idea where the problem may be coming from ?

Thanks