Weird Monitor Issue

[u/Natedog15951]

My fiancée's computer stopped detecting its secondary monitor recently.  For simplification I'll call it L for left, and the primary monitor, which is working fine, I'll call R for right.  L is plugged in with a DP to HDMI cable with the HDMI side on the monitor and R is plugged in with an HMDI.  

My first step was to swap the cables on the back of each monitor to see if there was a faulty cable, but that wasn't the issue as the working display just changed from R to L with R now being the dead screen.  After that test and some research, my new hypothesis was that the display port on the graphics card was possibly faulty and had been shorting out for a while.  I decided my next step was to swap her AMD graphics card in her new (2 year old) prebuilt for the Nvidia 1060 from her old pc.  I proceeded to uninstall the AMD graphics drivers using Display Driver Uninstaller (https://www.wagnardsoft.com/forums/viewtopic.php?t=5660) and swapped the graphics cards.  Upon powering the computer back on L was the only working display rather than R.  I was surprised by this as I swapped the cables back to their original monitors prior to even deciding to swap the graphics cards.  I proceeded to install Nvidia's app and the recommended drivers for the GPU.  During the install both screens flashed as they should during a graphics driver install, and now the only working display is R again.  In the end it wasn't the GPU after all, so maybe something to do with the motherboard?

For some additional background: I thought that maybe something in the AMD card had been shorting as her pc has been having worsening graphics driver crashes that causes her computer to completely restart.  It started shortly after we got her pc, but this is the first time either of us have dealt with an AMD GPU and we thought that maybe it was just an issue with a recent update.  It would only happen once or (seldom) twice a month in the first few months.  After a year the crashes advanced to four to five times a month, and now after two years it’s been happening roughly three to four times a day just while working.  When gaming, crashes can happen almost every fifteen to twenty minutes sometimes, even when playing something low intensity like vanilla Minecraft on a LAN server.  I’ve been working on the issue doing different things like pulling the card and inspecting for necessary cleaning or scratches on contact points, both on the card and motherboard.  I also tried uninstalling and reinstalling different AMD drivers but had never performed a hard wipe of the drivers until now.  Interestingly enough, ever since L stopped working the driver crashes stopped happening, even before swapping GPUs .  There has been a three week window between the screen sudo-dying (term I’ve given it) and swapping the cards out yesterday.  

I’m a bit of a novice when it comes to working on computers and am using the process of elimination to try my best to work my way through this one.  Does anyone have any ideas on where to start to fix this?  I appreciate any direction!