I am running my own server. Those are not example experiments.

Hi RotundSquirrel78
Could those be the example experiments ?
Are you running your own server, is it the saas free tier server?

RotundSquirrel78 if you can, I would appreciate it if you could attach the response sent from the server to the tasks.delete or tasks.delete_batch calls in the browsers developer tools under the network section

I don't get the error any longer and the experiments get deleted as expected. So no complains on my side...

What's the error you are getting ?
(open the browser web developer, see if you get something on the console log)