I was working on a team with people with various employment statuses. Contractors, employees of the client, and me as a regular full time employee of the company that “owned” the contract. My HR manager gave us a presentation about our reporting structure. I had at least seven managers for different reasons across various projects.

I got a new position so needed to resign but I had no idea which managers were the ones I should notify. I looked at the org chart that the HR lady showed. I sent my resignation to five managers that would be affected by my leaving. Unknown to me my project manager was actually a contracting manager hired by the client. He let his employer, the client, know that the lead dev quit.
Apparently it destabilized the contract for my employer. If I hadn’t just issued resignation they would have fired me for telling a customer about a significant internal staffing change. They didn’t fire me because the optics would have been worse for them.