Well, MaintainScrollPositionOnPostback is used in situations you actually want to persist position regarding last action. For example, you scroll down the tree and edit it's last item, but as it happens the handler of the NodeEdit event is on the server and the page postbacks. Without MaintainScrollPositionOnPostback set to true, the page will have the default scroll position.
A solution to your problem would be either:
1. to stop MaintainScrollPositionOnPostback;
2. if you need non-default scrollPosition, you can persist the position in cookie and on pageLoad (or even better on ClientLoad event of the TreeView) to restore it.
Hope this is helpful for you!
the Telerik team
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