Sherman had 76mm on mantlet, and 51mm on hull....
Also, the british 2lber and american 37mm could easily penetrate the side armour of a Panzer 4 or 3, which was just 30mm, with the british 2lber capable of of penetrating 37mm at 500 yards, and the american 37mm capable of penetrating 36mm at 500 yards.
Next, yes, in the game the Pz4F2's gun has always been quirky with the shermans, though normally it is always a one shot kill. Never been sure why. However, as a note, the Pz4F2 uses the KwK L/43, not the L48.