I see that the class name is CustomRadEditorCtrl
, which assumes that a customized RadEditor is being implemented. Such a scenario is not officially supported, and any possible side effects from customizing Telerik controls should be handled manually.
However, another major pitfall I see is that the version used is 2013.1.417 which is quite an old version and moreover, it is one released before the existence of IE11, and it is expected this version to be unsupported with browser that have not been available for testing back in time.
Try if using a more recent version of RadEditor resolves the issue.
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?
Telerik Feedback Portal
and vote to affect the priority of the items