Task Milestone Error Condition

Support,

I have created several Private and Invite only groups on my site.

In the Timeline entry window there is a list of items that the user can select from.
> Status Files Link Photos Task Events Blog Polls Videos

When a member of the group selects the TASK item, they are shown a message (attached image)
"This section will only be available once you create a Milestone"
CREATE MILESTONE (Button)

So the user thinks they need to create the milestone. You get an error condition (attached image)

NOW if the Owner of group selects the CREATE MILESTONE button they are taken to a page to create the milestone (attached image)

So it works for the owner, which make sense, but should give a warning screen that only the owner of the group can create a milestone.

Found this on an Invite Only group, but had the same issue on a private group.

Is this a configuration issue or a bug?
Thanks for the help.
Dan