First of all, this issue is already KNOWN and stated as "resolved" with a very roundabout fix HERE, simply removing some software from your PC that causes the device manager to refresh.
But what if I can't find what causes my DM to refresh every time? What if I can spend days without having this issue and suddenly in the middle of my A12 savage this start happening out of control wiping my entire party late in the fight because of something completely random in my pc decides to refresh the DM window and I take my time to look at DM window it has exactly the same items when it works perfectly while no issues(I took screenshots in days when I didn't have the issues and compared to when I have). I am 100% sure it happens when the device manager refreshes. I am constantly playing it with the window open monitoring it, out of nowhere it refreshes and at the same time my input in-game go out of control.The thing you need to now do is track down what is causing your "Device Manager" to refresh. To do this, is a long and lengthy process, but to get rid of the "obvious" go a head and update all your drivers to make sure you have latest. Once that is done, if you are still blinking, then you need to expand each tree element and note down the devices that are there. The "Blink" should add or remove one of these every time it "Blinks". You must keep going through all the items here and wait for the "blink" to occur and make sure that the item you looked at didn't disappear or reappear. Once you track this down, you need to figure out a way to disable it.
This doesn't happen in any other game I have tested it's only with FFXIV and the roundabout "fix" which requires monitoring MS Windows Device Manager doesn't help when you can't point out what is causing the blinks, refreshes, etc... on top of that MS doesn't let you know what is happening behind the DM window, no logs, no message, no way to know what's happening besides your wild guesses.
What bother me most is it ONLY happens with FFXIV and to see this issue as "resolved", which is not, after 3 years, 5 months, 7 days.