An isolated example will be much appreciated.
Could you check the browser console for errors?
Also, have you tried with another version of Progress® Telerik® UI for ASP.NET Core? May be an official one, as 2020.1 305 is an internal build.
Progress is here for your business, like always. Read more
about the measures we are taking to ensure business continuity and help fight the COVID-19 pandemic.
Our thoughts here at Progress are with those affected by the outbreak.