Thank you for the provided image.
I have tested the described scenario and I reproduced the exception with Xamarin.Forms
3.5 when RadListView and RadTreeView controls are used.
I have logged this issue on your behalf in our Feedback portal and you could follow the item on the provided link below:
You can find your Telerik points updated for bringing this to our attention. I can assure you that I have raised its priority and a fix for it will be provided in the next minor release.
Currently, the workaround I could
suggest you use the Xamarin.Forms 3.4.
Let me know if you have any additional questions or concerns.
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal
and vote to affect the priority of the items