had this with all of my Liberations ... after you click Liberate, you become all units from your opponent ... but some units stay in the barracks, airbases & seaports from your former opponent.
you can find and relocate these units only if you open the list "Reserve Units", leave "All Reserves" and double klick on the pretended units to center the screen on the barrack/airbase/seaports to see if its in your or in the opponent's ... then click "add to selected" and send it to your country.
Just bad ... the remaining AA will fire on the planes and i think there is a penalty to the relations.
Land Units can cross without fire.
... or just wait until a new opponent from your former liberated country takes his barrack/airbase/seaport
thanks
greets