KM/H to MPH problem (Zongshen ZS One / Lexmoto ZSX 125 / AKT RTX 150)

[Axle]

I recently bought a second hand Rieju Strada 125.
The bike is a rebrand of a Zongshen Z-One (2017 model ZS125-48A). Here's me thinking the bike was made in Spain! Other rebrands with the same speedo include the Lexmoto ZSX 125, Macbor Stormer 125, AKT RTX 150, and EVO R3 150 (among others).

I understand that the speedo model is SS183 manufactured by Chongqing Sansan Electric Appliance Co., Ltd., but I'm not entirely sure that variations aren't produced by other Chinese manufacturers.

I'm having difficulty switching the speedometer and odometer readings from KM/H to MPH. The unit only has one trip button. If I keep it pressed it seems to reset the trip and nothing else.

The speedo does have the capability to display MPH, as you can see below.

Owners manuals for these Chinese re-brands seem to be to be either non-exist or useless.

Any ideas?