The aftermarket oil shields are made with square edges rather than like the radiused edges of the original. This causes the interference.
That shield is not a high tech part. It is simply a rain coat to keep oil leaks form getting to the rubber underneath it. If you still have the old battered up one, you can weld up the rips and holes, and bang it into shape. You can use the new aftermarket one to figure out where holes go after you finish welding up the old one..
