Time Trigger causes HA to be not available

Hi,
I am newbee to HA.
I have configured an automation with time trigger.
As in the documentation Automation Trigger - Home Assistant
I wanted to trigger every 30 minutes.
I added in the Webgui “/30”, as described in the doc.

When looking at the yaml file I found 30 only.
I edited the yaml file and changed it to “/30” (including the quotes).

Now, when trying to change the automation via the weggui, HA consumes 98% of CPU time - which seems to be a loop.

How can I make the time triger work every 30 minutes?

Should be a time pattern trigger, and should look like this in the UI:

image

image

thanks for help!
At least, this was accepted - will see if it works.

In the yaml it was set as /30 (without quotes) although the docu says it has to have quotes.

So the quotes obviously caused the “loop”.