Program Monitor Panel closes

Last September i replied that Holly's fixes had worked, but within a few months the Program Monitor began intermittently disappearing again. Lots of trial and error and  vague circumstantial evidence, but it seemed to happen less when i just directly export individual spots instead of sending several to media encoder. Also, when directly exporting it seemed to only disappear on the first one, but then remain for the others. Still not always.
ANYWAY, saw the new suggestion of leaving the Frame IO panel open and that again seemed to work for about a week, but now we are back to it disappearing about 2-3 out of 10 exports. 
Maybe someday an update will fix all this.... 

Building and saving a new workspace from essentials work! Thank you!

I'm glad I could help! It was super annoying. It took me a while to find the solution. I will occasionally have an issue with it closing, but I'll switch to a backup workspace and it's okay.

thank you, you wonderful people.
Last week, my company took away my MacBook Pro and put me back on a PC laptop and i started having this (among other problems) and they are all quite annoying, but this was the worst. Holly's solution of going thru Essentials and saving a new Workspace Layout took care of THIS problem. Now onto other annoyances.
THANKS AGAIN!

OK, but I'm still guessing you had a pixel or two overlap of either the main window onot the 2nd monitor or from the looks of your screen shots (the red  x is slightly cut off) and I'm guessing you had a pixel overlapping onto the main monitor.

I have Adobe Premiere Pro (Beta) installed. I opened a project in it. When I click "Send to Media Encoder" in Beta, the Program Monitor does not close.

Okay, here's the twist: I was in the editing workspace when it worked. I thought, well, I set this up the way I like to work and save the workspace. I opened Lumetri Scope and Lumetri Color and rearranged the panels. I saved my workspace. When I went to export and clicked "Send to Media Encoder", the program panel closed...like I had clicked the red X.

Also, out of curiosity, I switched the screens, moving my main premiere pro screen to my secondary monitor and the program monitor panel to my main screen. When I clicked "Send to Media Encoder", the program monitor panel closed, just like in the other configuration.

I see the monitor until I click "Send to Media Encoder". At that point, the program monitor panel closes, as if I clicked the red X in the top right corner.

Well, I could finally get it to disappear when selecting "Export", by having either the main PP interface ever so slightly, even by a pixel, on the 2nd monitor. Or similarly, having the program monitor window, ever so slightly extending onto the Main PP monitor. In all cases, the monitor window came back when coming back to the Edit tab, from the Export tab.

I also tried these with the Lumetri Scopes on a second tab with the program monitor as per your workspace picture. It does look like your monitors may have a small overlap onto the others display.