Cheryl if your camera is one of the older vintage like a Mamiya C330 it may be the seals are going out on the back, might even happen on a modular back like Bronica and Hassys have. 120 film wouldn't show this effect until the seal is nearly falling out of the camera but 220 without the backing paper is vulnerable to the slightest leak in the seals. My old TLR had this problem and only showed up when the camera was at rest in a bright area. Rapid shooting usually never showed anything. It got fixed pretty soon after the discovery of the defect and never had a problem afterwards.