Thought I’d reply to a 2 year old thread, since a very similar issue happened to since the recent June2019 update and just in case anyone else has similar symptoms.
I have RPi3 running OSMC with TVheadend controlling a USB DVT-T2 tuner (Realtek/Panasonic). Passive cooling keeps SOC below 60degC (hottest is when running MMAL H/W H.264 decode even though CPU load is low). Been working fine for a couple of years, symptom since upgrade is Kore WiFi remote control disconnecting at intervals and the system info page on OSMC reports ‘busy’ for the WLAN for a period. RPi3Power supply can deliver 2A (load tested…). Red light on front of RPi says power OK, dmesg reports CPU voltage fluctuation only between 2s and 6s after boot up at point that USB tuner is being activated.
This thread gave me the idea to pursue powering as an issue even though the symptom occurred after a system upgrade and even though no under-voltages were reported by the dmesg command. Solution that worked for me was to power all USB peripherals through a separate powered hub and this seemed to do the trick even though I ran the hub off the same supply.