I put this in support since it also shows some bugs.
If you didn't know the Battle Viewer has been "fixed", check out this post https://forums.galciv3.com/464463 starting at Reply #13.
If you don't want to read it, then go to options and remove the check mark for "Trails".
The Story
I am the Iconian. The Krynn declared war on me, but they were too far away to worry about. Then this happened.

I now had planets, shipyards and starbases next to Krynn territory that I needed to defend. Before doing that, I checked the Diplomacy screen and found some bugs.
After surrendering, the Yor still exist in the screen.

After clicking on the Yor, the background vanished. After clicking on the Iconian planet (me), the background was still gone.
After a turn, the Yor were gone, and the background was still gone.

The background would come and go at various times in the Diplomacy Screen. I could get it to come back by clicking on the various display options at the top of the screen.
As the war picked up, I suffered a defeat without a ship being lost - or did I?

The graphics for the ships sometimes doesn't show anything or it shows the wrong amount.
Continuing with the war, its "Missiles Loaded", or maybe it's more correct to say "Missiles Launched." I just like this picture.

I like it even better when I'm attacking a planet.

There are problems with the previous two pictures. None of the missiles has reached the other ships, but the display at the top of the screen shows reduced strength for the Krynn fleet and the display of the ships at the bottom right has red damage indicators on the Krynn ships. These parts of the display are not wrong. They are just out of sync with the animation.
I attacked another planet with a moon.

It really was a moon and not something else, and I won easily.
I had trouble with some planets being invaded over and over by the Krynn and by me. I tried building up the defenses to try to defeat the invasions.

This time the Krynn only have a 71% chance of winning. Is it enough?

Yes!
After that I decided to call a temporary cease-fire, save the game and take a break.
I will be submitting tickets for the bugs mentioned.