I'm a little surprised that the Sat 800 would generally outperform the
R-1000, but anyway...

On the day the R-1000 had the 'edge', had either it or the 800 changed
position or orientation in any way? I'm wondering if, on this
particular day, you were using the R-1000 in a location that is quieter
than where it's usually situated.

Was there a change in the way either radio was powered?

I could be wrong, but I have the sneaking suspicion that something is
keeping the R-1000 from performing to its full potential most of the
time.