In general in order to persist any changes made on the client after a post back the trackChanges
client-side method should be used, otherwise the changes are lost. This is mentioned in the following help article here
under the Preserving changes
Regarding the problem described in your post, we would need to examine the exact implementation used in order to conclude whether the experienced behavior is a bug or not. Could create a simplified version of your real world scenario and post it here?
All the best,
the Telerik team
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