'Mac OS' disappears from 'Optional Tags' when I click in the 'Optional Tags' field

While composing a prior post, when I clicked in the Optional Tags field with ‘mac OS’ displayed to see what other tags were available, ‘mac OS’ no longer appeared in the listing, even when I returned to the document and tried again.

For the current message, I don’t even see it displayed as a selectable ‘optional tag’.

Mac OS 10.14.3 (Mojave)
Only Office v. 8.0.1
Desktop Editors / Free Edition

Hello @mk7z

Please record a video demonstration of you actions that lead to such behavior for the reference.

@Constantine This isn’t something I can anticipate happening. The ‘Mac OS’ tag was preselected when I was composing the message. I clicked in the field to see what other tags were available (also, to see whether more than a single tab can be selected). I saw the Mac OS tag disappear. Clicking back in the tags field it no longer displayed. In other words, I couldn’t add it back.

I wasn’t able to reproduce the issue according to provided description. macos tag can be added freely to the topic. If I’m missing something, let me know.