I'm not running LineageOS, but I think I've cracked it, which leads me to believe that it was caused by wear and tear on the charger cable. As I mentioned previously the cable I was using wasn't clicking into the port. Over the last day and a half I've been using another cable, which does click into the port and the battery has actually charged while the handset is in use even when watching streaming TV and HD videos.
In conclusion I'm wondering if the worn 'C' connector wasn't making contact correctly and maybe causing arcing rather than a reliable connection.