Help Troubleshoot My Bizarre Monitor Issue!

I’m now 15 years removed from my days as a hardware/software support professional–and hadn’t ever run into anything remotely like this anyways–so wanted to open this up to folks that are still in that game. Or in the electrical engineering game. Or, I suppose, in the game of letting Mllz know that he’s a freakin’ idiot for not considering such-and-such obvious solution to the problem at hand.

Description of issue:
A few times a day, my computer monitor goes black for a few seconds (and occasionally longer) when the door to my office is opened. It’s not every time my office mate or I open the door, but the opening-of-the-door is the only thing that seems to trigger it. The monitor doesn’t lose power while it’s blacked out, nor does it appear to lose the signal altogether (when this particular monitor loses the signal from the computer, the power light changes immediately from blue to orange; in these outages, it stays blue).

The facts:
[li]Monitor is a ViewSonic 23" flat panel, about 4 years old, raised about 5" off the desk on a metal monitor stand[/li][li]Computer is a 2013 MacBook Pro running OS X 10.9.5 and also Win7 via VMware Fusion[/li][li]3’ HDMI Cable connects the two[/li][li]The door is heavy, steel, and windowless, 30" wide and maybe 9’ tall. It opens into the office, coming within about 2’ of the laptop at the closest part of its arc.[/li][/ul]

I’ve tried jiggling both ends of the cable, the computer, the monitor, and the desk, to test for loose connections or bad cable, but none of these replicate the issue. Nor does it happen when I deliberately try to replicate by opening the door repeatedly. Doesn’t happen to my office mate at all, though he’s got a completely different setup (and, of course, doesn’t occupy the same physical position in the office as me).

I haven’t tried swapping out the HDMI cable yet because my spare is at home, and, well, when I’m at home I’m simply not thinking about my troubleshooting a pesky issue with my work monitor. So I never think to bring it in. But you’re all right here, and can probably provide advice that does not require me to write myself a note on my hand!

So what gives? Electromagnetic thing due to that steel door moving? Air movement from the door opening? Or just a cable/connection thing that doesn’t reveal itself by the standard jiggle test? I’m totally cool with replacing the cable and/or monitor, just don’t want to do so unnecessarily!

[li]Are you running wireless? Your office mate?[/li][li]If wired, are you able to connect to your office mate’s connection, and vice versa, and test?[/li][li]Have you considered moving your set up to your office mate’s location and vice versa just to test?[/li][li]Are you aware of any significant electrical junction on the other side of the door? Plasma ray-gun in test mode perhaps?[/li][li]How old is the building? Timber frame construction? Concrete block walls? Metal 2x4s? Is the door frame loose? Was the door changed lately, resulting in removing the door from the frame (thinking screws in the door frame touching poor wiring)?[/li][/ul]

Thanks for the reply, Duckster!

[li]Both of us are running wireless[/li][li]N/A[/li][li]Definitely considered switching workspaces temporarily, but wanted to rule out other things I can check myself before inconveniencing him. Our respective walls are whiteboards that we both make regular use of and we’d be in each others way.[/li][li]Nothing unusual on the other side of the door, unless you consider a dozen or so headphone-wearing programmers unusual. Oh! And the Ecto Containment Unit in the office next door, but that’s probably irrelevant.[/li][li]Building is brick office building, probably 1960’s or 70’s. Door is pretty tight in the frame, although frustratingly not square. If I had to guess, the wall the door is on is not original to the building, but rather an artifact of when this floor was renovated to its current use–probably within the past 10 years. Given the lack of exterior windows in here, I suspect there was not a private office in this particular corner until fairly recently. And given how much sound travels from the adjacent offices, probably not the highest quality renovation job either.[/li][/ul]

In the interest of less-dramatic testing, I’ve moved the laptop to the other side of the desk to see if that makes a difference in frequency of the blackouts. And while doing so, I noted the following behavior that seems rather relevant: when the MagSafe power supply briefly disconnected, a similar, but more severe blackout occurred. The monitor went black and did not return at all until I opened the laptop back up. Two observations:
[li]The monitor did eventually display the No Signal message and change the light to orange, but it took several seconds (so it may indeed have been losing the signal all along, but it had been generally been restored prior to the monitor letting me know[/li][li]Didn’t even occur to me that losing power temporarily might impact that HDMI output. We seem to have increased the number of potential failure points here. Booo.[/li][/ol]

If it’s not the cord or the monitor then the only other thing would be the gpu. Does it have a discreet graphics card? I don’t know how Macbooks are built but could the connections have come loose somehow?