We have faced the same error thrown due to a bug fixed after 2015, see FIX: "System.FormatException: Input string was not in a correct format." thrown on Chrome when browser is zoomed in/out. Back then the issue has been related to an error in the parsing of the scroll position when Chrome is zoomed in/out.
Since this issue has already been resolved I would ask you to clarify which version of Telerik Control you are currently using. In case you have an older version (before Q1 2015) you can try the suggested workaround in the comments below the feedback item linked above.
If this is not the case, It would be very helpful if you share the declaration of the RadTreeView along with the related code-behind logic so we can have a better overview of the current case and try to pinpoint the problem.
Looking forward to hearing from you!
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