Thank you @fullboogie and @trempa92 for your responses. In my case I have multiple models connected to my NVR, some of which are 2386G2s, 2385G1s & 2347G1-LUs. Confusing thing is that whilst the 2385G1s & 2347G1-LUs are all working without any issues, it's not that the 2386G2s are all faulty...