I have 2 devices with one of them freshly re flashed with CSSU latest stable version and kp 52 installed and both work with no problems, in my opinion I think your problem is the location of the injection drivers which has been standardized as mentioned by StefanL on the post above I quote "Location of the injection drivers has been standardized to /opt/packet-injection-modules/(kernel versión),", so check if the injection drivers are in the above location, hope that helped.