In what way? Do you have evidence of your claim? Police flatly refuse to release damaging footage to the public, often turn off or obscure their range of view, and yet somehow these cameras are always running in good working order when they capture incriminating evidence on a suspect.

Police do those things because the camera is effective. The solution here is to punish officers for disabling or obscuring their cameras, not to get rid of the cameras.

It's the DRM argument - publishers don't stop using Denuvo because someone always manages to crack it, they use it to stop little Timmy from copying Assassins Creed 27 on to a USB drive for his friend Dave. In the same way, Officer Porkchop can't openly conspire with Lieutenant Bacon to plant evidence, because the audio is on record. But doubtlessly, the Porcine Patrollers will manage when it really counts, maybe just not as often.

well the first level, any evidence collected and released is more than zero, which is the baseline before cameras. They are frequently included in trials. They are also sometimes released to the public in high profile cases, usually in the interest of exonerating the police, but which is also sometimes informative.

Do you have any reason you do you think that they are a net negative?

The only centuries old effective way to police the police is to have watchmen for them. In ancient time, they have society assassins that will hunt down entire police families (including extended one over several decades). This is usually misrepresented as family feud. The best example of this was how entire family/clan of China first emperor exterminated with the instigation of one of Chu (a country destroyed by first emperor) originated eunuch. You need to have a society element carrying illegal extermination to keep police or rulers in check.