Slide show is not showing the right orientation

Ha ha! Nope, there's no such identification for these kinds of things. Maybe there should be.  As far as when it might be resolved, that depends on how difficult it is to fix. That's something that I have no clue about. [I did take a class in basic about 40 years ago, and I've not done any programming since! :>)] But fixing bugs does have a triage like hospitals; crashes, like heart attacks and gunshots, get higher priority while cuts (that are not bleeding profusely) are much lower down the pecking order. Also, easy fixes that are not likely to cause damage elsewhere are more likely to be fixed than if you do this "one simple thing" that causes everything to fall down. So, the quick answer is I do not have a clue, hopefully soon. It has been reported to the high authorities. 

Whenever I do scanning, I always try and start with something with text or a known issue (is the right-handed person wearing their watch on the right hand (then oops!). That way, I can set all subsequent images with the same side of the slide or negative facing up.

What I found with photographing slides as opposed to scanning is that photographing slides is significantly faster, and scanning slides gives you significantly better quality. When I started out digitizing my "just under" 10,000 slides, there was no way I could do all that in my lifetime; it just takes too long. But I also know that not every one of my slides was outstanding (yes, hard to believe, but true). So, as I occasionally go through the digitized slides, if I find any that could benefit from a proper scan, I do that scan.

As far as your wish to work with DNGs, do understand that if you take a 12–14 bit image of a slide, it becomes a 12–14 bit digital image of a 6–8-bit slide — and no more. If you take your camera and photograph a white sheet of paper, that image has that shade of white — period. To try and increase the dynamic range of an image, I've tried to use SilverFast's double-scanning approach, but I've yet to see any significant beneficial result. Also, while I did not mention it specifically, I did photograph my images in DNG (that's all I ever have my camera set to shoot), but still, if I wanted the best quality image, I had to scan the slide because scanners capture a greater Dynamic range than cameras can (but fewer f-stops). Nonetheless, while a JPG image has more dynamic range than a slide, I'd still continue to shoot raw because there are other things I can do with that raw image. But expecting a greater dynamic range is not one of them.

Consider the following data (from https://www.photoreview.com.au/tips/shooting/dynamic-range-explained/)

Below, in the chart, "D" can be defined in several ways:

Dynamic/Density Range (D) = log10 Intensity Range (Lux)
Dynamic/Density Range (D) = Colour Depth (bits) x 0.3 (where 0.3 is log10^2)
Dynamic/Density Range (D) = Exposure Latitude (f-stops) x 0.3
Therefore, Colour Depth (bits) = Exposure Latitude (f-stops)

And the following are some use-values of "D," (this is a partial list from the above-cited article).

So, you can see part of where scanning can achieve a better scan, but again, no better than the original content.

Gad, that was a lot more than I planned on writing, I got carried away. This whole thing is very interesting to me.