Good evening Nicolas and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the featured image of your calendar not being even.
I would love to help you with this topic.
However, to be able to do that, I would need 2 things.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Secondly, I cannot take a look at your calendar currently, since it requires login credentials. Would it be possible to gain temporary front-end access ?
Have a good week-end,
Geoff B.