I would recommend connecting your LG TV to the internet for the sole purpose of installing any firmware updates. WiFi would be the easiest probably. Then after you update you can delete the WiFi off the LG.
I have read several articles that elude to HDMI cables/connections or firmware capability can cause the issue you're having. That said if you have never updated the LG it probably needs to be even if it doesn't resolve issue.
I update my older Samsung at least every six months.