Say QA dumps a badly tested release which causes a lot of weekend drama for Prod and QA does not own up to management or apologize to Prod (e.g. they did it under pressure from Business or Marketing). In retaliation Prod doesn't approve releases after Wednesdays. I've seen much worse than this.

Prod probably doesn’t even think of this retaliation; they just think they’re acting like the sensible adults in a company that just needs to “become professional” here.

A lot of company red tape was thought to be green tape when implemented.

Yea, this sounds like the sort of problem described by Patrick Lencioni

So people becoming defensive because they are not treated honestly, while everyone is afraid of doing mistakes.

That's when it get outright toxic. What is much more common is just all the gaps between solid silo walls.

By measuring the task load?

Edit: to be clear, I'm not saying any delay that isn't caused by high utilisation is attributable to malice. Just saying that if you've narrowed it down to those two, you've done the hard work. Those to are very easy to tell apart.