Seems a common problem with this game, I've had it in the house set up since last Thursday, and turned off since then until I can solve this as I'm not a huge fan of metal fragments knocking around the playfield.
The lower pop bumper can impact the crystal ball lane guide, they actually made a new version of this part with a cut section on the crystal ball lane as you can see, but it doesn't address the other problem where the pop ring can impact the front corner of the guide.
I can see three possible solutions, would appreciate feedback on the best to go for.
1) Top right is to cut into the pop ring a bit. Word of advice here getting the tree bracket off is a nightmare due to super-super-super strong thread lock. Worried this will compromise the strength of the ring, it's possible for the pop to come down on the ball just past the position of that hex post. It wouldn't hit the actual cut area but it would be close.
2) Bottom left is to basically copy what JJP did on the middle of the guide and cut a small section out. Concern here is balls coming off the upper pop which will hit the rubber in the bottom left of the image and bounce it straight into the guide. Will dropping the height weaken it sufficiently for the ball to bend it.
3) Bottom right is bending the guide which may make it easier to have the ball to hit the edge head on from certain angles.
I noticed over the weekend the upper pop had something to collide with too - the witch protector bracket corner. Thankfully that one is a no brainer, you can just cut the corner off, theres loads of needless metal there with zero chance of a ball ever hitting it.