I remember Nationwide as beset by technical difficulties - Michael Barratt in London would hand over to Leeds or somewhere, but there would be no signal, or the remote studio would not be able to hear him etc.
Something else which seemed to happen quite often, and not just on Nationwide, was the soundtrack on a filmed item gradually going out of sync with the visuals.
Then there's the oft-repeated Nationwide clip featuring Bob Wellings conducting an interview beside a line-up of people dressed as judges, one of whom faints. Bob was not sure what to do, made some remark like 'could someone get her a glass of water', then carries on with the interview.