I think I had to buy the 1/4 bushing set from Woodcraft. I had to do some searching to find them. As to a bit hitting the bushing. That is a function of centering the base on the router, which requires a centering cone. The cone has a shaft, which you place in the collet, then fit the base down on the cone until it meets the router's bottom. Put the bolts in and it's centered. If the removable base comes loose, it can shift and the bit will hit the bushing.
Unless something else is going on, re-centering the base is the first order of business.
The more I do, the less I accomplish.