The frequency issue I believe is hardware related:
https://z-wave.me/products/uzb/
It is likely that the real issue regarding the frequency is because of the antenna inside. Their latest products like the Razberry 7 Pro, the physical card is the same, the antenna that it is shipped with is different based upon the frequency.he UZB comes in three different versions depending on the transmitting frequency used:
ZMEEUZB: Version for all frequencies around 868 MHz (EU, Russia, India, China — default is EU).
ZMEAUZB: Version for all frequencies around 921 MHz (Australia, Brasil, Japan, Korea — default is Australia/Brasil)
ZMEUUZB: Version for all frequencies around 908 MHz (USA, Israel — default is USA)