I'm not in the industry anymore, but every time I raised an issue to the boss that got ignored, I used to like to keep a little folder where I'd print the emails or just take notes about the issue, the proposed fix, and when and why it got rejected.

Then, 8 months later when everything is on fire, I could point at the date February 12, where at 3:40 PM I raised this specific issue that got ignored.

It never benefitted me, not once, in fact I sincerely think my boss at the time thought I was a smug little prick. Which was fair, I was one. But credit where it's due, every time I brought the folder back out, he'd get a look like he just swallowed a mug full of cold piss and tell me I was right. That's all I really wanted out of that folder anyway.