I've created a new job with the new UI / feature enabled.

I managed to create one task with a new job cluster successfully but when adding a second task with a new job cluster and trying to save it I received the following error:

Error updating [JobName] - Either new_cluster or existing_cluster_id must be specified.

I've yet to try something similar with the API but seems to me I cannot even create a second task with anything other than an all purpose cluster.

Any idea what I might be doing wrong, has anyone had similar issues with the new feature preview?