That is likely the issue. English and Italian use the same number of threads per inch and the same diameter, but the thread sharpness or cut angle differs. This is why one should not swap back and forth between the two.
Look at the freewheels and the hubs for inscriptions such as "BSC," meaning ISO or English threading.
The 1980 or 1981 Ofmega rear hub and Regina America freewheel that came with my Bianchi definitely seem to be Italian-threaded, so I leave them paired together (currently on the 1959 Capo) and swap my various Japanese freewheels around on other hubs I own.
__________________
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069