None of those serious issues are intrinsic problems with public sector unions, though. Most of them would exist even without the union playing a role, and a well structured union could also be preventing them.
Cops not being able to be fired is 100% because of the union. Every time they negotiate a new contract and the city tries to put in the ability to fire people the police refuse to arrest anyone.
Well, we don't need to get into details, but most pro-union folks I know don't consider police unions to be workers' unions. Either way, as I said, it's not an intrinsic property of unions. It's that way because police unions exist to hold the public hostage, not because unions are bad.
Holding the public hostage is an intrinsic property of public sector unions. That's the leverage they hold. If they don't like the deal being offered they can stop working and because their roles are so important that holds the public hostage.
That's how strikes work in general, whether the job is public or private. Transportation is mostly privatized, but if the workers strike we're all going to feel it to some degree. That's the point.
The difference with police unions is that they work in the inverse - we're in danger when they do work. Police hold us hostage by doing their jobs (badly) and offer mob-like protection.
I'll also just that I see the police union as a perfect example of what I called a US mafia style union. In Nordic countries you can't behave like this and get away with it in a union and there are pretty strict rules for what is and what isn't a legal strike.