OK, about the Wifi/Bluetooth/2.5mm and other questions that came up in the last few pages.
Cayin N5ii has 2 modes of operation, a regular mode with Android app support, Wi-fi, Wireless Bluetooth, and Audio Priority Mode which is "pure audio" mode where Wifi and BT are disabled to provide the best audio performance. You can enable/disable Audio Priority Mode by swiping notification bar down to see available shortcut options.
The initial N5ii firmware release (v1.12en) is in a special mode where in addition to manual switch between Regular and Audio Priority modes, it also automatically switches to Audio Priority mode as soon as you connect 2.5mm HO. This is not an intended permanent functionality, it's only a part of the initial FW release and in a few days Cayin will release a new FW version where this feature (automatic switch to Audio Priority mode) should be disabled, allowing you to manually switch between the modes.
So, no reason to panic that something is wrong with your N5ii hardware