@StevePAM - Good catch! I actually have a bug open for this myself and will update this post as I hear back from the support team.

If I assign the assignee again I then get the option to the remove the assignee and it works.

That is exactly the workaround in this case.

If I open the card details pane, the assignee shows as assigned but X to remove the assignee is covered up by the toolbar. I cannot move the toolbar.

I had not previously noted that, but I will add it to the ticket.

You can click the button at the top next to the close X icon and it will bring you to center view, which allows you to remove the assignee. Hopefully they fix the main issue soon so you don’t have to add an extra step, but there are options to work around. 

@Melina Kingsley This is not working for me. Maybe I’m misunderstanding the steps you describe. A static screen shot or animated gif would help.

@StevePAM - Here are screenshots…

If you have your cards opening in side view, you can use the switch to center view action:

To end up here, where you can access the remove assignee action:

I created a support ticket for the following issue:

Remove assignee action disappears when card no longer selected (719381

Note: The issue of not being able to unassign someone when the card is open in the side view appears to have been resolved:

Update from Miro support:

Thanks for reaching out and reporting the issue about the card assignee. 
 
I could not reproduce it myself, but my colleague experienced the same issue. I will report this to the team in charge, and I'll update you as soon as I have the feedback. Please bear with me!

Here’s the response from the support team:

The team advised me that currently, this is a low-priority bug, and they do not have immediate plans to fix it as they have more urgent tasks on the roadmap. Thus, unfortunately, there's no ETA to be shared.