Hi Joost,
Thanks for using Syncfusion products.
We would like to let you know that we have already provided the support for iOS 64 bit version. We request you to download the latest Syncfusion Xamarin Studio from the following link.
https://www.syncfusion.com/forums/118366/essential-studio-2014-volume-4-service-pack-2-release-v12-4-0-34-available-for-download
Please let us know if you have any questions.
Thanks,
Magesh Kumar K