Premiere displays 480i channel in 16:9 only

On my TiVo Premiere one of the SD alternate locals (but only one of them) will only display zoomed in 16:9 widescreen (as if I had chosen the "Full" aspect ratio on the TiVo Zoom (Aspect) control). If I press the Zoom button repeatedly the onscreen legend cycles through Full/Panel/Zoom but the displayed aspect ratio never changes. Other 480i channels display as expected.



Anything I should try?