There is only two ways to fix this that I have found.
The easiest is to use a scope with a duplex reticle, and turn it 90 degrees counterclockwise so the windage turret is now elevation and elevation is now on the left side and adjusts windage. It doesn't look traditional but has the advantage of making the loading port more accessible for single loading etc. And you can mount the scope very low.
The second way is to have a skilled machinist make an extractor claw with tighter tolerances. The issue is the slop between the edge of the rim and the extractor claw. If the claw doesn't fit tightly, say 0.005" clearance or so, the case starts to move upwards as it is drawn backwards and hits the ejector blade. That upward momentum overcomes the sideways motion that is desired. The extractor claw must fit tightly with just enough clearance to always snap over the rim of the case when the rifle is loaded. I fitted two Sako 85's with new, tighter extractors and the problem was permanently and properly fixed. Both my M85 .375 H&H and the M85 7x64 eject perfectly sideways now. BUT nobody is doing this as a commercially available solution. You'll need to luck out with a machinist who will take on the project.