No this is definitely an iOS bug and from what I have seen over the years diff people have diff issues. Not everyone seems to have the same bug. That particular blank message bug except for saying delivered and the iMessage header with time carried over from my 7 plus to my X and from iOS 11 on up thru 10 betas, then 11.0.1, 0.2, 0.3, 11.1, 11.2 beta 1 and 2.

Heres a google search with articles on the buggy iOS 11 topic. [Link: google.com]

I've had another bug for awhile where you go into photos... tap the share arrow and type in the persons name you want it text it too and it'll hang there for eternity. Gotta force quit and try again.

I wish i had a link to an article I found before where someone found like 600 user interface issues in iOS 11 and document them all. While maybe not bugs, it was mind blowing. Wrong placement of this or an error with that, wrong font here, etc.

Here is another issue. For the last 6 years Wifi Sync with iTunes just never f'ing works. For anyone I know. Airdrop is a piece of $hit too and rarely works properly.