I work in third tier support. I mainly handle mobile device management and IAM tasks, but I also do advanced desktop troubleshooting. If a problem gets big or is extra important our desk side support hands over an issue to the team I'm on.

In January 2019 I was handed a super special problem that dominated my next 45 days.

Microsoft Word was flashing. Worse, it would often crash at the end and there was no document recovery available. Trust me, we looked. This problem was causing people to lose work. This meant big money was being lost.

The symptoms was the user was just normally using Word and all of a sudden the document would blink. No, not Windows, no not the entirety of the Word application, just the document portion itself. I first saw the problem on a video and couldn't deny what was happening.

Sometimes it would flash only once, but sometimes the whole document would continue to flash on its own. There was no interaction with the PC and it's sitting there continuing to flash. It was like the document is being used by a DJ as part of a show as a flashing light effect. At that point Word was gone, you had to crash it.

At this point what we knew is it would start to flash in response to doing something. We knew nothing.

We had a hunch it was caused by one of our Word add-ins, we have a number needed for business and compliance reasons. But we ran down patching, drivers, our Windows build. Everything.

I opened tickets with every vendor. We talked about their product. We talked about drivers and hardware build differences with our hardware vendor. We even went so far as to ship hardware with our custom build to one vendor. We brought in an expert from Microsoft into the office to work alongside us.

For weeks we couldn't figure out how to repeat the problem so we couldn't figure out if certain changes would fix it. We confirmed it wouldn't happen every day for every user, someone might never have the problem happen again.

Then at one point we got ahold of a laptop with the issue happening over and over. We gave them a new laptop and used this access to finally identify how to repeat the issue on any computer.

To recreate the problem on demand I would make this insanely complex 1000 page document with hundreds of formatting changes. Then I would do what I could only describe as being like a 3-year old. I would violently scroll up and down in the document until it would start to flash. I would change to a second document of similar complexity and scroll in it the same way. I would change to a third one, and so on. I could watch Word's memory use jump as I did this sequence. I could usually count on the flashing beginning when it reached an approximate point.

By this time we had limited the problem to Windows, drivers or one specific add-in that had to be on the PC for the problem to happen.

Approximately one month in we finally identified the actual problem. We needed to have hardware acceleration On in Office. We had disabled it.

We identified the specific add-in vendor that had recommended it be turned off. They couldn't explain why it needed to be off beyond vague reasoning that it fixed some problem they couldn't give the exact details on.

Proving that sometimes your entire problem comes down to that one checkbox. It's kind of anti-climatic but if you work in IT you've been there.