Hi @Renato Shimose ,
I couldn't reproduce this issue on my end. And as per your description, I am assuming that the related settings on your site are totally correct and you didn't miss anything. Have a try to clear the browser cache and restart the browser or change a browser. If the issue still exists, I'm afraid there may be something wrong in the backend which is controlled by Microsoft and we have no access to, it appears that something is going on where the CSS isn't being applied correct or some script isn't running as expected. The quickest way to solve this issue is to new a service request in Microsoft 365 admin center, then let Microsoft CSS engineer help you check from the backend.
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