Thank you for the provided information.
Currently we have an issue logged in our Feedback portal reporting a crash with Telerik UI for Xamarin controls when upgrading to Xamarin.Forms version 4.0 and here is the link:
Workaround for the crash
I could suggest you downgrade the Xamarin.Forms version to 184.108.40.2064807 or higher version of 3.6.
Regarding to the "When Updating Xamarin Forms to version 4.0.x.x the ListView hangs the UI and loads very slowly
"? Could you please elaborate more on this? For example this behavior observes when upgrading to Xamarin.Forms v4.0 but with the previous versions of Xamarin, the RadListView behaves as expected. For further research the case I will need more information on the exact setup you have. May I ask you to send me a sample where the issue could be reproduced or how the RadListView is defined.
Note that in the forum only image attachment are allowed. If you want to send us a sample you need to open a support ticket and attach the project there.
Let me know if I can assist with anything else.
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