Computer ONLY boots with certain combinations of display outputs

[DailyCakeSlice]

Lately I've been having trouble getting my PC to boot, depending on which monitors are plugged in, and where. I've spent so long scratching my head on why this is happening. For some reason, certain combinations of my monitors being plugged into my graphics card stops my computer from starting Windows, while others work just fine. I'd love if anyone can take a look and maybe help me understand what's wrong/how to fix it.

 

I have two monitors that I use. I'll give them colors to correlate with the image.

Pixio PX276h ("blue"). 1440p, 144Hz, HDR (which only seems to work with HDMI?), which I use with DisplayPort (the HDR is crappy anyway)

ViewSonic VX2250WM-LED ("orange") mounted portrait, an old 1080p 60Hz monitor. Only has DVI and VGA, so I'm using an HDMI->DVI adapter.

 

When it works (green check mark, or a different monitor plugged in to any DP output)

• Both monitors turn on if I have both plugged in.
• My motherboard cycles through debug codes and stops on 04, which is not defined in the manual, or A0, which corresponds to "IDE initialization is started".
• The "orange" monitor will start with the motherboard logo, and then the windows logo (both on their side because the monitor is mounted portrait).
• Windows loads up as normal.

When it doesn't work (red x)

• Only the "blue" monitor turns on
• My motherboard cycles through debug codes and stops on AE, which is defined as "Boot to legacy OS"
• The "orange" monitor never wakes up, while the "blue" monitor never displays anything, and just loops falling asleep and waking up.

What I know so far

• The "blue" monitor works just fine when plugged in through HDMI. But I only have 1 HDMI port on my graphics card, nor a DP to DVI adapter, only HDMI to DVI, which my "orange" monitor uses.
• It's not the DisplayPort cables, I've had identical results with multiple different name-brand DP cables
• Spamming DEL and going to the bios, and exiting ALWAYS brings me into Windows with ANY combination, but only once.
• Turning the "blue" monitor off completely, and then back on and starting the PC ALWAYS brings me into Windows with ANY combination, but only once.
• I tried my friends monitor, with all 3 DisplayPort ports, with and without the "orange" monitor plugged in, and it worked every time.

Here's the different combinations I tried, and whether they worked or not:

 

My PC specs

• i5 6600k
• Gigabyte GA-Z170X-Gaming 5
• 32GB RAM
• EVGA RTX2080 Super Black
• 970 Evo 1Tb, along with another SATA SSD and HDD
• Newest drivers/firmware on everything

 

I am genuinely at my wits end about what is causing this or what would fix it. Does anyone have any suggestions? Thank you all in advance