It will always work, though

i do its on very low, but some cops still do the animation thing when they're stunned by feedback

It's always 100%. Do you have some reduction in animations?

well i really dont see the cops getting stunned when i enable the feedback, it sounds really useful but doesnt really work for me, is it a chance to stun cops or what?
oh also i have seen a bulldozer get stunned by feedback.

ECM Jammers have their functions in loud.

ECM Feedback will stun all cops (except bulldozers and cloakers) and if there's a SWAT Turret on the map, it will turn it against the cops