Blanks screen, no audio for BBC3 alone. All other channels fine.
As BBC3 had come back onto freeview I retuned my set top box, a Sony VTX D800U and checked 23 was a channel received on the Tivo. Both recorded BBC3 programs, and live TV through the Tivo showed a blank screen and no audio. When you first changed channels to 23 on the Tivo it did show for a few seconds then blanked. If you used the Sony remote to bring up the D800U settings screen when it was on channel 23 BBC3 played behind the settings menu but as soon as you exited the settings menu it all blanked again. The TV tuner received BBC3 normally. Using my spare Tivo, spare D800U and an old TV I duplicated the setup and it worked fine. As far as I could see all settings on the Tivo and D800U were the same. I unplugged the Tivo and did a cold restart; I returned the TV to factory settings and setup again, no better. In desperation I unplugged the D800U, plugged it back in, and all works normally, I didn’t do a retune, just unplugged it at the mains.
Only posting in case someone else has a similar problem, yet again “switch everything off at the mains” works.
Chris