Hm, I'm not sure what you mean.. if you mean that while the item is being recycled (actively being recycled, with the green progress bar and everything), it gets pushed into the output slot? Or do you mean, while you are putting the item in the recycler, it gets automatically pushed into the output slot?
If it's the first one, then that doesn't seem possible, and if it's the second, then that is unfortunately unintended behavior; but for either one, you could try disabling the "auto ingredient push setting".
This setting is meant to automatically push items whose recipes produce 2 or more of the item (like belts, etc) after a certain delay, but it's an imperfect hack that sometimes pushes items to the output slot when it doesn't really need to. When it's disabled, if you DO get an item like that (1 piece of belt in the input slot, without a second belt on the way), then it will 'clog up' the input slot, not allowing anything else to be recycled.
