The MRX 720 is shown as the Audio Device is MC, isn't it?
With a similar problem last year, the TV (a VIZIO E-Series 60” Class Razor LED™ Smart TV | E601i-A3) was showing up as the Audio Device, as per the image below. I don't think that is the issue here, but just wanted to check, since you and Jmone are on the same drivers with different results. Maybe your FHD Samsung TV is part of the problem.
That image is from a couple of posts above this post:
https://yabb.jriver.com/interact/index.php/topic,117404.msg813453.html#msg813453 You may want to do a little light reading through that post and thread to understand a bit more what is going on.
BTW, what model is your FHD Samsung TV?
Also, how do you control the NUC? Do you use a wired keyboard and mouse, a wireless keyboard+mouse, use a Remote Desktop application into it, or use a Remote Control App?
Regardless, try this, if you have one of the remote control Apps (See below), or can get one. Well, anyone can get Panel, so I guess that is an easy answer.
1. I assume that you have the NUC set up on boot to start MC with Windows? If not, do that, in MC Startup options. With or without Media Server, but with Media Server turned on and note the Access Key.
2. Set up a Playlist with samples of each of the formats that aren't working now. Or all formats if you wish.
3. Make sure MC is still set to play in WASAPI Exclusive mode, as per above testing which didn't work. Make sure that the "Player" Zone points to the MRX 720, just to make things easier.
3. Get the App you are going to use, if you don't already have one, and check that it will connect to the server and play files in a Playlist to the MRX 720. Test with a format that you know works now.
3. Shut down, and fully power down the TV, AVR, and NUC.
4. Disconnect the HDMI cable from the MRX 720 to the TV, leaving the HDMI cable from the NUC to the MRX 720.
5. Restart everything, and wait a few minutes for everything to settle down.
6. Use the remote you selected to connect to the NUC MC Server, set the output to "Player" or the MRX 720, open your Playlist and test a format that doesn't normally work.
Did it work? Try all the formats. Do they all work now?
If all the formats worked now, then the problem is your Samsung TV, and the HDMI chain. MC is being told the capabilities of the TV instead of the MRX 720.
You just need a Remote Control App that can connect to the NUC MC Server, can send output to the MRX 720 Audio Device, and plays at least one format.
On another PC
Panel in a browser, which is probably easiest, and allow you to connect to a MC Server, and select play to "Player" or any Audio Device on the Server.
Tremote
iPhone
Panel in a browser.
JRemote if you own it. No trial version. Although I have never used that, so I'm not sure how easy it would be to use for this testing. I assume it would be fine.
MO 4Media for iOS if you don't have any other App. It has a free version that will play three songs in a Playlist. Enough for testing, with just a restart of the App to allow another set of three to be played.
Android
Panel in a browser.
JRemote for Android if you own it. No trial version. Although I have never used that, so I'm not sure how easy it would be to use for this testing. I assume it would be fine.
MO 4Media for Android. Same trial version restrictions as above, but works fine for this testing.
Gizmo