I know the problem well, and there are solutions.
First, I want to say I have a WDTV Live Plus (older one like the Hub), so when I started to view iThing photos/videos sent to me I had the same problem. It is caused on Windows and other non-Apple devices, because there is data in the file that tells an iDevice the position of the camera relative to where the controls on an iDevice were positioned when the video was taken so an Apple device can get it right when viewed on the device. Older Windows and WDTVs did not have the “secret decoder” and are clueless.
Some of this is improved today, although my Win 7 sees the iDevice photos and videos in the same wrong orientation as WDTV, my Win 8 has no problem; same is likely for your Win 10.
Some mobile apps get it right, too. Examples are, the Roku app that can cast photos and videos in the iDevice to the Roku/TV. When the same photos and videos are copied to my new model WD NAS, and viewed from my Win 7 they are still whacked out, but viewed from NAS using the WD My Cloud app on an iDevice, the photos and videos are positioned correctly. So, the point being is, success in many cases depends upon what program or app you are trying to view them with, and on what equipment.
OK, these newer methods work well for me today, but say you can’t use these above options, and you want photos/videos that are only on your WDTV Hub (or attached drive) to show up correctly on the TV. The solution I used early on was to convert them with a free program I found called Free Video Flip and Rotate. It worked very well, but it meant rotating and re-writing quite a few video files.
The version on my PC is a few years old, so I just went looking for a current one, and I found it at the website of the maker, DVDVideoSoft. So download it at link below and install it on your PC. I see from the screen shot it now has the Help built into program; for my older version I needed to download a separate Help file.
Let me know how well it works for you.