.... I guess saved game could help me a lot to see what's up exactly.
Attaching a saved game (might need to add .txt to the file name to get it accepted).
I can't reproduce the intermittent failure of selected unit to blink in a small game,
but have found some other issues with gtk3.
This game is saved at end of turn. On starting the next turn, the Chinese
want to open a dialog. On accepting, the negotiation window is empty in gtk3 !
Attaching screen shots for gtk2 & gtk3. This is much easier to reproduce than the
empty battle dialog, but may well be a symptom of the same problem.
Another issue I noticed with gtk3 only. When completing a research item, a list
of available items to research next is presented. Shift clicking an item brings
up the manual page for it as a separate window. In gtk3, this window does
not respond to its close button (top right of the window).
Not critical, but the close button should work of course. (End of turn closes it.)