it's definitely technical difficulties.
In case you have the Now & Forever or Live Days from Wembley bootleg (straight from the BBC broadcast of the show), you can hear the guitar sounding weak up untill the switch point mentioned above.
The VHS/DVD guitarpart is overdubbed to mask the technical difficulties. It's even visible in the intro part where Richie tabs but you hear a chord (or vice versa, haven't seen the show in ages)