Just really letting the readers here know that there appears to be a bug in replying to Reviews.

There's a few businesses reporting it at the GMB Forum.

Essentially, owners / managers reply to a review but after they submit the response it disappears.

It's been escalated within Google, but obviously any additional information is always handy for engineers to fix a bug. So if you, or your clients are experiencing the issue maybe post it over on the Help forum to provide more examples.