After a firmware upgrade I've learned to do a reset of the TV. This varies with each model but for reasons we only can guess, a factory reset gets it all setup again with channel scans and more. It's a known thing to do with most models.
Just had a software upgrade to 04.27.09 and now the telly when you change the channel it goes to the selected channel then after 15 secs goes blank for 5 seconds. It also will suddenly switch itself off and then back on again at will......anybody's telly doing the same.

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