Big World: 1942 v3 Game Rules
Game Version 3.8
Attached is the game in question, but in Round 5 for the Americans (Human player), in the combat move section he moved his bombers initially 1 move into a sea zone, moved some other pieces, and then finished (still during the combat move turn) 2 of the bombers into Japan. After combat, the 2 bombers should have had 2 moves left, but it showed none and they had to be destroyed as they couldn't leave the bombing territory.
I think it is probably due to the fact he moved them one, moved others, then came back and finished the bomber moves (still all during the combat move phase), but shouldn't be a problem to do so.