The default state of the Kendo UI Grid with detail template is collapsed to ensure better performance by means of lazy loading the details. When the master grid is refreshed, it assumes its default state and this is what happens when the grid is filtered - it is refreshed and the detail rows collapsed.
To persist the expanded/collapsed state of the grid, you may use the approach we have shared in the documentation:
Let me know if you have any questions in regards to the article.
Get quickly onboarded and successful
with your Telerik and/or Kendo UI products with the Virtual Classroom free technical training, available to all active customers. Learn More.