I have had this problem during the last month.
Manifestation of the problem is easily replicated when in the last drone and under attack. Most times occurring in the tail gun and under fire from enemy.
A possible related side issue also seen is when having a gunner in the plane, the gunner is discoed when the second drone is destroyed.
The original pilot seems to not disco in the case where a gunner has been disco'd.
I have had this occur in several bombers, b26b, b24, lancs, for sure.