220 film is known to be more susceptible to edge fogging and my own experience supports this. It is not specifically an issue with the backs
(though a leaky back is a leaky back, period). It is a film issue. You need to be careful that loading and unloading are done in subdued light- though inevitably I find that sometimes the deepest shade I can find is that cast by me and thats ok providing you really do keep the film in the shade at all stages till the back is closed up. It will also help to give the tail of the roll a good tug when you remove it from the camera and before sticking down to make sure its wound really tightly. You might still get a little fogging on the edges but handled with care there should be no reason to expect it to intrude into the frame. I also return the roll into its packaging after exposure- whether this serves any purpose or not I don't know

Unlike one poster above I do think 120 is much less likely to edge-fog than 220. However a high proportion of my slide film usage is 220 - because of its convenience- and clearly if fogging was a major uncontrollable issue then I could hardly do so.

Personally I would rather put the film in the hand-baggage X ray machine than take it out of its wrapper before I want to use it. My experience in India is limited to Delhi but I had no trouble getting a (cursory) hand-inspection of rollfilm pushed back into its foil sleeves there.