Editing newsletter issue puts it into orphaned category

I use Simplenews with Mime Mail 6.x-1.0 to create and send my library newsletter. I have it set-up (through Views, filtered by Term ID) so the most recent issue displays as a page view on the current issue page and all previous issues display by title on an archives page view.

Sometimes I have to go in and edit the issue after it has already been sent. I have been able to do this successfully, using this version of the module, for quite some time.

My problem is that every time I edit an existing issue of my newsletter, it somehow places it into the "orphaned newsletters" category which means it no longer displays on my current issue page.

I have updated core and a couple other modules since the last successful publication of my newsletter.

Thanks in advance for your help!