LG TV, Xfinity Stream, Weather Channel Issue

LG TV. Xfinity Stream. Everything working as expected EXCEPT ... recently (June 2 or 3) on both our LG TV's the Weather Channel HD (270 and 1102 in our area) will not start up; it times out with the message "This Video Can Not Be Played, TVAPP-00100". Weather Channel HD works fine on Xfinity Stream on iPhone, so the problem is LG TV. I've discovered that the non-HD Weather Channel works (39 in our area). I have tried all the things LG or Xfinity support would tell me to do; in my experience they always blame the user: turn things off and on, check cable tightness, check for the most recent versions, restart gateway, yada, yada, yada. This is likely caused by an Xfinity Stream update that conflicts with something LG. (Remember when LG/Xfinity was stuck on 'closed captions' for three months?) This may (or may not) get resolved by an update in the coming days, weeks, or months, but until then I will watch the non-HD channel. The problem is, in my experience, for whatever automatic secret helpful non-helpful reason, all non-HD channels will "blip" on the hour and switch over to HD. I recall several years ago I found a post that gave instructions to tell the app to NOT switch to HD. This is in the Streaming app, so the settings are limited. I have looked everywhere (Accessibility and Picture Mode for the LG Settings; Accessibility and Playback Preferences within the app). Where is the setting to turn off auto-switch to HD channels? Or is it gone forever?