The recoil operation was violent and often resulted in poor primary extraction.
As an automatic weapon’s chamber and barrel heat up with prolonged automatic fire, the resulting excessive temperature can cause a chambered round to “cook off,” or ignite without intent of the gunner. As a result of firing from a closed bolt, the Breda 30 could not fully take advantage of the cooling properties of air circulation like an open bolt weapon would, thus making cooked off rounds a realistic hazard.[4] The disastrous results could lead to potential injuries to or even the death of the gunner.
https://en.wikipedia.org/wiki/Breda_30