Watch receives messages but replies don't send

I received an iMessage that showed on all my devices – iMac, iPad, iPhone & watch. I selected a reply from the list of smart replies on the watch and sent it ... or so I thought. I later checked the conversation on my other devices and the watch's reply wasn't there. So I replied from my iMac. This reply appears in the coversation on all my devices, including the watch.

So the conversation looks the same on all my devices, except that an extra reply, supposedly sent from the watch, appears on the watch before the reply from the iMac.

The watch gave no indication that the process had failed and apparently it thinks the reply was sent.

Has anyone else seen this? Any suggestions different from the ones for "If you can't send and receive messages on your watch", because it's receiving messages fine?

Thanks in advance,

Steve = : ^ )