Missing Troops: If your troops lose the battle in one round, that happens. They're scattered and will return in 4 hours + travel time if there are survivors.

Port: You can't hold an inactive's port. The capture just allows to fight the fleet there. If you aren't getting a CR, the port is empty.

Kaleg is right. If your troops weren't enough to survive first round, you will not get a combat-result, but instead the message "your tropps has been reported missing". Send a larger army, and make sure you have enough to take the wall down

wall can cause much damage I once found an inactive 700K player with a lvl 30+ wall

Pillage battle will be lost when that inactive town is occupied by 3rd player, You need liberate it 1st.
I know this coz it happened to me also.