It's a v4.26 bug. And I believe the race dropdown is to blame. You see, my recently-conquered neighbours (a methane-breathing race) have a little over 10 million more people than I do (normal humans), and as a result my empire has gone from being 100% human to 49.8% human, 50.2% Vostockian. The race dropdown (on both the Ctrl-F2 'Race Details' widow, and the F9 'System Info' window) keeps defaulting to the methane-breathing surrender monkeys instead of the proud, noble humans who seek to enlighten these savages and make them productive members of our glorious Empire, no matter how may times I select 'Human'. I am certain 'Vostockian' was the default way back when I gave the order to train the HQ unit. *sigh* Why must it be so difficult to oppress the masses?
I can see this being a problem in other areas as well. I'll bet the species for your new ships and the species for any new populations are Vostockian too 
. I probably need to have some type of 'dominant species' flag for those Empire where a minority species is the primary one.
I have changed the various locations in the code that currently use the most numerous species to instead use the dominant species. This is initially set to the founding species. I'll add some way for the player to change it.
Steve
