Hi Roberto,
We have already found and fixed the mentioned issue with Schedule Appointment rendering in MonthView in Xamarin (Android) and included the issue fix in our latest Essential Studio 2017 Volume 1 Service Pack 2 Release v15.1.0.41 and is available for download under the following link.
We have prepared simple sample based on this scenario, please find the below sample.
If you face issue with this latest version, could you please revert to us by modifying the provided sample based on your scenario with more details, it will be helpful for us to check on it and provide you the better solution.
Regards,
Subburaj Pandian V.