Yes, a number of people (including me) seem to have found that the range of the 3080 is less good than the 1081. Only time will tell whether there is some error in the design, or if it's just due to normal production tolerances. They do appear to have changed the software because it now searches (not necessarily a good idea) when the transmitter signal is "lost".
Maybe a starting point is that the display unit is smaller than previously, so the aerial (proabably just a wire inside the enclosure) is "folded" more. If you're prepared to open up the unit, then straightening the aerial (and making it vertical) might help reception. There have been a number of posts on this general topic (although IMHO some have not been technically very accurate).
I wasn't expecting too much of FO's attempt at the UV Index figure because it requires a precise measurement which is strongly "weighted" to the UV wavelengths that cause skin damage (basically UVB). However, I was surprised how consistently bad* all the units seem too be, when FO appear to have engineered the solar unit quite well. They haven't just "bodged" the luminance and IR readings from the PV cell output, there is a light detector under the hemisperical diffuser (to the right of the PV cell) and (probably) a UV sensor at the front to the left of the PV cell.
I haven't been able to find any UV sensor which even physically looks like the one fitted by FO so I don't know what the spectral response might be. A UVB sensor is moderately close to the required UV Index response, but it seems that most UV Index sensors use a special filter (which maybe FO have omitted to include). The response at 325nm (not far from the UVA/UVB boundary) needs to be just 3% of the sensitivity at 295nm (just in the UVB band), see Wikipedia.
*Here in London mine has reported an index of 10 with a not particularly clear sky and 7 indoors (behind window glass and net curtains). It's generally considered that UV does not pass through glass (although it does depend on the type of glass), an Index of 7 is about as much as I'd ever expect outdoors in London, and I certainly don't feel in danger of suffering sunburn/sunstroke at home indoors.
Cheers, Alan.