I wonder if the paint has changed shape. Those were the days of solvent-based paints. They can be gassing off for a long time. I bet Rollei expected that the back would be opened in a relatively short time after they close it, box it up, and send it off to be sold. Maybe sitting closed for so long so soon after manufacturing led the paint to melt a bit, expand strangely or some other defects to grow as the last of the solvents hung around. Or other solvents from the packaging seeped in.
Examine the back/body interference area. Look for any change in the paint surface. Rub it down with some safe cleaners- alcohol, maybe a little Windex? See if you can 'polish' the paint in the area a bit? Start in the middle and do testing before using something that could affect the exterior paint!
I've never had the experience of dealing with a new in-box Rollei TLR. Maybe this kind of minor binding was designed in, and it will relax after a few uses. I've seen a fair amount of variance in the 'clip' action of the back, from almost no friction to binding. I know people who have forgotten to close the latching mechanism on a Rolleiflex, shot a roll, and had no light leaks! The clip action is not an accident. You might find a particular angle for pulling that leads to quick opening.
As shutterfinger says, the back is relatively weak and prone to bending. It is possible to increase or decrease the interference, and I fine tune backs all the time. But I wouldn't suggest you attempt this in any fashion in this case, at least not before a few months of use! I would hope that Rollei knew how to package their cameras to avoid damage in transit and stocking, but again I doubt they were expecting the camera to sit for 50+ years in the packaging!