All mpg, mov, mp4, etc. files have no video showing, just sound in ThumbsPlus program

Hello Codec People,
I am using ThumbsPlus (cerious.com) for many years now, and using the current version,and Windows 10 (1909), and lately my mpgs show a black screen, though perfect audio. I had the same problem in 2018 with an older version of ThumbsPlus, and a K-Lite Mega PAck install fixed everything, but not this time.I think the problem developed after installing and then uninstalling some other software. WMP, MPC, VLC, etc., all play them fine, but not my ThumbsPlus.
The reason I brought my prob here is that I noticed somethign very strange, and wondered if it might point towards a solution.
- First off, I double-click an .mp4 to open & play in ThumbsPlus, and I get audio loud and clear, but a totally black screen.
- Leaving that "black" file open, I double-click another adjacent .mp4 next to it, and it OPENS and PLAYS correctly! I can then double-click additional .mpg files, and they all will play correctly, and they will all keep playing even after I shut down the original non-playing file.....BUT....though the ones I'd already opened were playing correctly, I couldn't open any additional movie files correctly without having a fresh, non-playing one open again first.
I hope I've described it clearly enough. For some reason, as long as I have a D.O.A. mpg open in the program, any additional mpg files I open WILL PLAY NORMALLY, so it seems to be something about the initial loading?
I've tried multiple uninstalls and reinstalls of ThumbsdPlus AND K-LiteMegaPack, but nothing gets fixed. I've sent a report to ThumbsPlus just now, but don't have high hopes for a solution to come from them.
Again, all plays fine with every other player, but I LOVE ThumbsPlus, and really want to solve this.
Question - Will "resetting windows foundation" possibly fix it? Will a full reinstall of Windows fix it?
Thanks to all for reading this, and hope there is an easy fix somewhere .
John

This is a compatibility issue between Windows 10, NVIDIA, and they way that program renders the video. In short, legacy overlays are not supported anymore. The problem is not related to the codecs that are used.

The second instance of the application works because only the first instance uses the broken overlay method.

Some more information here, including additional workarounds:
https://codecs.forumotion.net/t3470-another-workaround-for-black-screen-with-audio-issue

Thanks for the response. I do have NVIDIA graphics, and ThumbsPlus got back to me today also, and said that a fresh install of Windows, and/or ThumbsPlus, wouldn't fix a thing, though my PC and NVIDIA graphics card and ThumbsPlus played together perfectly before the registry got jumbled up somehow.
The only available fix available from ThumbsPlus is that I can install another type of player (as a custom button on their toolbar), which I did with the MPC player, and it works perfectly.
Otherwise I just open an mpg file that stays black - stop it from playing  the audio, leave it sitting open, and then open the same file again, and any others I want, and they all will work perfectly.
Thanks again for taking a peek at it for me.