What is the vintage of the two problem switches? I had an early (circa 1996-97) MTH RealTrax O72 remote switch as part of a floor layout that did the same thing, except with all of my locos, not just one. I don't believe I ever identified the cause of the problem. After a while the rails became heavily pitted from all the sparking. That switch is in a landfill now. I might have gotten $30 or $35 for it on the 'Bay, but I didn't want to pass the frustration on to anyone else in the hobby!!
Some other things to check: Are the problem switches LEVEL (in both the direction of travel, and side-to-side across the rails?) Is the switch's base plate "floating," or under torsion because it was fastened down too tightly to the platform surface? Do the swivel rails have excessive play compared to your other RealTrax switches? Something about these two is different, you just have to find it. It's usually a lot of trouble to remove and replace switches on a permanent layout. But swapping a couple around would be another way to experiment.
The SD70 is a long loco. If it follows usual MTH practice the innermost axle is a "dummy" with small, unflanged wheels. At one point i think these wheels were even made of plastic (which is a good thing, to prevent short circuits!) Personally I've never been a fan of the dummy inside axle for performance or appearance. With this design, the functional truck wheelbase defined by the outer two axles is very short. This makes the trucks prone to weaving and bouncing. So I'm not surprised that this loco is picky while your Geeps, F-units, etc., negotiate these switches uneventfully.
One last thing to check... is the track leading INTO the switch aligned straight, or does the loco enter the switch at an angle? I tried to watch your video again but it's a little hard to follow. IMO using your phone in landscape (horizontal) format works better for this sort of thing. Keep troubleshooting and post your results!
