Mine originally had this. It was ramping off the playfield on the back side of the Monger lid. I added a single washer under each screw to fix it. For very fine adjustment, you can GENTLY bend the Monger bracket from underneath the playfield.

It's okay for the back of the Monger lid to be very slightly higher than the playfield. The front can be very slightly lower. Flush is ideal. You just do not want any lips from the front that can cause the ball to launch with a strong shot off the flippers.

Game plays perfectly now.

Yup! Mine had huge airballs off Monger when I got it. Thought I was going to break something.

On mine the cover was not sitting flat, so you could feel the playfield sticking up at the edge of the cover. The cover was too high at the front, and too low at the back. I removed the cover, raised the Monger by hand, and bent the bracket holding the cover a tiny bit using a couple pairs of needle nose pliers. Put the cover back on, measured, back apart and bent it a bit more again, nailed it. As soon as the cover sat flat, the airballs disappeared.

I really thought it was going to break something, or rip up the playfield at the back of the Monger hole, so you definitely want to take care of that.

Your top plate on monger is not flush with the pf. Adjust it with the screws on the plastic. Use a straight edge to help.

There is also actual adjustment screws under the monger mech. It will let you level the whole thing.