Are there any instructions, or panels that you can open with test switches? There might be screw adjustments under the platform, or there might just be software adjustments in the electronics. I'd REALLY try to get info out of the manufacturer, if none of the panels you can open has anything inside.
If it can't be adjusted, then you could rip out the existing sensors and controller (or just controller) and put in a micro-controller of your own design, which could adjust in software. That's a bit of work, however.