I experienced a similar problem but that was only in the stock version. I had taken some SS and posted them in the UBI forum almost 2 years ago. Unfortunately, I can no longer find them on my PC and have to assume that I deleted them. The problem involved a rediculously large number of enemy aircraft that would seemingly spawn out of thin air, somewhere, well west and slightly north of Midway, well out of the range of any land.
My SS showed, literally, no less than 50 aircraft and during gameplay, I always seemed to run into them in the same spot during early war years. The planes would spawn several at a time, in an endless loop, sometimes crashing into one another (there were so many) and then would disappear east of me or after returning to their original vicinity.

When I first began playing the game, I attributed the massive spawn to one or more carriers that I suspected in the vicinity. However, repetitive attempts to locate these suspected ships proved fruitless. It wasn't long thereafter that I suspected a bug. Afterwards, I plotted a course that would simply bypass the area altogether.