Just to make things clear. You have a RPi that has a USB hard drive plugged into it as well as NAS that it has access to over SMB. This RPI has UPnP enabled and you have three LG smart TV’s that could access this RPi (literally) yesterday with the TV’s built in Video player. Today everything works exactly as it has before except for one TV is not seeing the UPnP server. In the period of time between when you last used this feature on this TV and when it stopped working there was zero updates or changes to any network equipment, the RPi, or updates to the TV. Is this ALL correct?
As for the view issue please post a picture. You seem to be referring to a view different than what I was thinking. I was referring to the movie and tv show menus with the assumption you were using the poster or shift view.