I have a similar issue on a Nikon D7500. when only the Unleashed device is plugged into the camera, it works well (especially after the upgrade to the latest firmware version). when I plug in the USB cable in addition, the camera becomes uncontrollable.
I cannot do anything with it any longer. it seems like it's powered off but isn't. I have to power off the camera, remove the USB cable and power on the camera to make it work again.
before the firmware upgrade, I also did have the "cycle" issue as described by user djf.
to me it seems like the cable itself is causing the problem, the camera more or less shuts down immediately when I plug in the cable.
I will need to produce a video of the behavior and raise a support case, as soon as I
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