With the Breda 30, Its numerous design faults teamed up to make it an extremely unreliable weapon, especially in the desert conditions of North Africa. The gun attempted to use a blowback system of operation to reduce complexity, but using simple blowback for a high pressure rifle round required the rounds to be oiled to prevent them from being ripped apart during extraction.
This didn't always work, leaving the front part of spent casings hopelessly jammed in the chamber, plus the oil attracted dirt into the working areas of the weapon, causing another type of jam. Furthermore, the gun used the same bad idea as the Chauchat with an open magazine that invited even more dirt into the operating mechanism. Also, the closed bolt design reduced air circulation and also put rounds in the chamber at risk of cooking off which could injure or kill the gunner.
Oh, and, uh, the magazine was non-detachable, making use of special 20 round strips to reload it which had the effect of drastically slowing the rate of fire. So even when the gun actually managed to fire one would wind up spending most of their time reloading it. he worst thing about the Breda 30 is that it was not the worst weapon of the Italian Army in the war. That would be the Fiat-Revelli Modello 1914 heavy machine gun: designed before World War I, it had the same problems as the Breda 30 (unsurprisingly, the Breda 30 is based on the 1914), was water-cooled (increasing the weight), had an oil pump to grease the rounds (thus making it even more complex and heavier), and by 1940 it had been out of production for twenty years, thus adding the troubles of age and wear.
The issues were ironed out with the later Modello 1935, an improved model with air cooling, no oil pump and, most importantly, belt-feeding. Except it jammed worse with un-oiled rounds, so they had to put back the oiler.