The cause of this problem is the standards for Solar Panels, that has the outputs measured at 25C so they are comparable with each other. The specification sheets for panels do list their peak voltage in other conditions but all the advertising is based on the standard. Solar installers know about this and size accordingly but your average consumer doesn't and is very quickly going to get into trouble with this.

I think what Delta needs to do here is accept that the standards mean all Solar will be sold this way and appropriately oversize the inverter so that it can cope with -10C sunny days. Yes its annoying for them but the reality is devices sold to people who don't know how all this works need to compensate for lack of expert knowledge in its user base.