Just looked at a new out-of-box Godzilla.

Playfield pitch exactly 5.7 degrees.

Not every three-ball lock, but if you get a few more balls through the lock it would 'lose the ball' and eventually go into ball search.

This is what I found:

I ran some balls through the building until one didn't register.

I shut the game off.

Gently, I took the other balls off the top of the building. I wasn't worried about these.

Then I lifted the playfield up a little, and I could hear the ball roll backward and settle on the upkicker hole, where the opto's would have been able to see it. There wasn't a 'drop' sound, so I knew that the ball was not resting in the metal trough leading to the upkicker.

All of this isn't visible, but I believe my machine would have a ball come in at a rapid rate of speed, hit the back of the upkicker channel, and come to rest on the lip where the trough that feeds the upkicker assembly is just a bit higher. This is just out of sight of the optos.

I use Felt furniture moving pads on the bottom of leg levelers, so I have these all the time:

https://www.lowes.com/pd/Scotch-24-Pack-1-1-2-in-Beige-Round-Felt-Pad/1000093217

They have remarkable adhesive. I cut a piece a little less than 1/2 inch wide. These are about 1/8 to 3/16 of an inch thick, which matches the 'drop' of the trough that feeds the ball to the upkicker assembly.

The 'little less than 1/2 inch' piece allowed the ball to easily drop fully into the hole where the upkicker rod is, and almost gave the ball no place to go except where it should end up... in the hole, blocking the optos.

I then tested 30 times. No failure. Then, of course, something not so good. The ball hit, I could hear it rattle and the upkicker fired ?early? And the ball was somehow in there and the normal ball search couldn't dislodge it. I had to lift the playfield to get the ball where it needed to go... though you could probably lift the front of the machine if this happened while the glass was on.

So I'm not sure this is a fix.

I think if I were in my shop I'd have made a small wedge shaped ramp out of plastic or metal to guide the ball to the upkicker hole.

Something about 3/16 at the tall side, tapering down to provide a ramp, a little less than 1/2 inch deep and an inch or so wide. Really good double sided tape to apply it... making sure I've prepped the surfaces for the tape with an alcohol pad.

If I end up going back on this service call, I'll post here what I did for a better solution.