I loaded my old save few turns before the actual invasion and played in a similar way as before so I have re-created the whole situation.
You can find saves as well as screenshots under following link:
https://drive.google.com/drive/folders/13oVj7Dsp5WjfwRbvoHTvLflHDNb-aXBr
Please note the screenshots are from 2 different invasions on the same planet - like 2 forks from 1 game.
If you load the game from uploaded save all you need is to press "idle ship" on bottom right corner of screen and invade the planet next to ship.
EDIT:
Not sure if this is relevant but I start the game through Steam. Bought Base game with crusade and intrigue DLCs on humblebundle - played the initial campaign map then i decided i'll buy retribution and bunch of other DLCs and after that I started playing a new custom game with custom race. Was thinking that my files might be corrupted somehow because of all these DLCs.
I mean the rules were totally different in the campaign map than in maps from other DLCs and custom maps after DLCs install.