Hi Dave,
Zeva are still offering support for existing customers. See here
https://www.zeva.com.au/Contact/
I believe the touch screen used is a HY-TFT320 and there should be some calibration buried in software/hardware, probably not user accessible. Or there may be a hardware failure of the screen itself. It's about a 50USD item.
Otherwise, I guess as a direct replacement you'll need to get another BMS with CANbus.
If you want a more generic BMS then have a look at Sergio's thread.
https://www.buggiesgonewild.com/showthread.php?t=160302