Myself and a friend have been working on this issue for quite a while now, and have come up with a new diverter assembly that on the games we've tested has completely fixed the issue. Both left and right orbits work great all the time, and no issues with the ball going into the VUK. Another nice aspect to the fix is the diverter can be replaced from under the playfield in 10-15 minutes, so there's no need to remove the ramps or upper playfield.
We wanted to gauge interest before taking the plunge of having these manufactured. We think the price will be $95.
Please PM me if interested.
Here is a quick video:
The video shows some left orbits, right orbits and right shot to the VUK, as some fixes inhibit the VUK access and/or right orbits.
Added additional videos
Diverter removal/install (this is what it will take to install):
More orbit tests (in test mode):