Display format

On SD channels which I know are now few and far between my Wally keeps defaulting to "stretch" but I would like normal (with the black bars) instead.

My options are normal, stretch, partial zoom, zoom along with gray bars. How do I get this to save? My settings on the receiver under TV are 1080/16:9. Not sure where else to look?

I've tried again and again to switch modes but the minute I turn off the Wally it seems, stretch mode returns.

The HD channels are not an issue.

Thanks