Hello Andrew,

A possible reason why this might be happening is a slow SignalR connection. What we do to prevent the default tooltip from showing is to change the title attribute with a data-title attribute to preserve it - we remove the title attribute when the Telerik tooltip shows, and when it hides - we restore it from the data-title attribute where we stored it. If the connection is slower, the default tooltip might show before our operation is complete.

The general reasoning behind the slow SignalR connection is the physical distance between you and the host - in this case, our demos. Could you reproduce the same behavior when using a Telerik UI for Blazor project locally? A possibility is to use the WASM flavor so that the application is single-threaded. 

That being said, I am marking this Bug Report as "Declined" because it generally stems from behavior that we cannot directly control.

Regards,
Svetoslav Dimitrov
Progress Telerik