Thank you for writing.
Since all the nodes are getting collapsed, it seems the tree is updated/refreshed. If you know when this happens or what causes it, you can save the tree state (expanded nodes and scroll position) and restore it afterwards.
If you have issues achieving that, I would suggest that you open a support ticket, where you can attach your or a sample demonstrating the undesired behavior
. Once we have it, we will be able to investigate a look for a possible solution.
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