Computer monitor blinks on and off when playing movies

I have an AOC monitor that I have had connected to my Windows 7 PC using the VGA connector for a couple years now, with no issues. I recently switched to using the HDMI connection, and am experiencing a rather odd problem. Now, whenever I try to play a movie on my PC, the screen goes black for maybe 3-5 seconds, then comes back for 3-5 seconds, ..., and keeps blinking on and off like this. Not only does it do this when streaming movies on Netflix/RedBox/youtube, but also when playing a DVD with Windows Media Player. And it will keep blinking on and off until I either close Media Player (for DVDs) or close the window/tab when streaming a movie.

I have only encountered this when playing movies - for some reason I can stream other types of videos on youtube just fine. It seems to be independent of video resolution, since I have streamed HD videos (>= 720p) with no problem, but then had the monitor blink when playing a 480p movie on youtube. Even stranger, it doesn't even seem to be the length of the video that is the issue, as I am able to play some rather lengthy documentary videos just fine. I don't understand why playing a full movie has this effect, but other types of videos don't.

I have done all of the following:

1. Changed the Input source to "HDMI" in the on-screen monitor menu.

2. Verified that the HDMI cable is secure on both ends, and even tried other HDMI cables.

3. Confirmed that the device is working in Control Panel (the device status for the display/graphics adapter says "This device is working properly.")

4. Attempted to update the device driver, and it says "The best driver for your device is already installed".

Lastly, I connected it to my work laptop (Dell, running Windows 10), and did NOT have the problem when streaming a full-length youtube movie. So, I don't believe that the monitor is defective, since it seems to work fine with the Dell laptop, and in all scenarios other than playing a movie. I'm not opposed to buying a new monitor if necessary, but I would feel pretty stupid if it turned out that I just needed to toggle one of the countless settings in the Intel Graphics Control Panel to correct this (I have experimented with changing some of them, but no luck so far).

Or even worse, I buy a new monitor and continue to have this problem 😫