Copied from the Radeon system info
Radeon Software Version - 16.9.2
Graphics Chipset - AMD Radeon (TM) R9 380 Series
Windows Version - Windows 10 (64 bit)
System Memory - 24 GB
CPU Type - AMD FX(tm)-8350 Eight-Core Processor
Samsung Syncmaster 2333 - DVI
LG 24M35 - DP to DVI or HDMI w DVI adapt (Doesn't matter same problem)
Samsung S22C450 - DVI
So the monitor IDs are inconsistent between the AMD drivers and Windows. Windows reads the GPU ports in the order DP HDMI DVI-D (bottom) DVI-I (top). The advanced Radeon settings read the same. But the normal driver does not. The Radeon interface reads in the order DVI-D DVI-I DP HDMI.
In center blue is the advanced interface, in the bottom corner is the windows display and in the top corner is the normal Radeon interface.
Note: When I took the picture, I had the SyncM on HDMI to make the screenshot make a bit more sense since the actual ID order I run is 2-1-3 as the LG is my main display, being in the center.
Unfortunately, I've only had 3 monitors for a shot time so I cannot say if the problem was present on older versions of the drivers.
So because the IDs don't match between the driver and windows, this is causing the very few programs that support multiple separate displays that I have to simply get borked, or worse, not even work anymore when trying to use said option. And yes, this issue is what's causing them to not work properly. If I disconnect a monitor to align Windows and the driver IDs they work perfectly fine.
Now I will admit that I'm pretty much close to just putting a second card to just get done with it but... I shouldn't have to. This is clearly a bug that shouldn't be there. And it's not even the fact that I use adapted cables or adapters that cause the problem (even though the DP or HDMI port are used on the card, the driver will still read DVI because it's the monitor's port. Meaning the driver reads all tree monitors as DVI ports, regardless of the output used). As noted in my screenshot, the cable used were all on their own and the HDMI port was still IDed improperly.
So how would I fix this? Besides a second card.