This method doesn’t work for me. I didn’t even have the Calendar access activated. Activating, deactivating, and re-activating the Calendar access didn’t help.
The search started to hang since the introduction of the new search feature. This issue happens only on my work computer, where the macOS is modified by my job for security. Maybe my job put some restrictions on Spotlight and it is causing this issue, but I am not sure. The Agenda search works fine on my personal computer.