These are fixed callipers, so there's no bushing or slide. Calliper seems firm, and it's fine now I could put a wrench on it I suppose, but I'd have to pull the wheel.I had a similar parking brake issue with my WK. Intermittent vibration; hot brake on one rear wheel. Happened once every few months. Caliper not sticking. What I found was rust flaking off the 14 year old parking brake shoes jammed the actuator. New shoes/springs hardware fixed it. But your issue is on the front. I’m wondering if the caliper mount is loose or the caliper itself is slightly loose. Caliper bushings? What about those nuts that hold the rotor to the hub?
These are two piece rotors, so yeah, there are a pile of what appear to be 10mm nuts that hold the disc to the hat. They all look tight, no idea what torque they are supposed to be at , but I'd think if they were loose it would be somewhat obvious.