branch softwarewire - third instance problem

[sqztom]

trying to get 6 sensors on 3 buses ( BME280 allows two addresses on I2C bus)
/code minimized to show problem /
code below not compiled with linker error:

ltrans0.ltrans.o:(.rodata+0x1a): undefined reference to BME280I2C::WriteRegister(unsigned char, unsigned char)' ltrans0.ltrans.o:(.rodata+0x1c): undefined reference to BME280I2C::ReadRegister(unsigned char, unsigned char*, unsigned char)'
collect2.exe: error: ld returned 1 exit status

commenting out any of lines :
SoftwareWire BusI2cX(a, b);

and both Arduino and PIO finishes fompilation flawlessly
Only two instances allowed ? why ?

/* BME280_I2C_SoftwareWire_Test.ino
https://github.com/finitespace/BME280/branches */

#include <Arduino.h>
#include <BME280I2CSoftwareWire.h>
#include <SoftwareWire.h>

// SoftwareWire softwareWire(SDA, SCK); - define three buses
SoftwareWire BusI2cA(22, 23);
SoftwareWire BusI2cB(24, 25);
SoftwareWire BusI2cC(26, 27);

//BME280I2CSoftwareWire bme(softwareWire); // Default : forced mode, standby time = 1000 ms
// define three instances
BME280I2CSoftwareWire bme1(BusI2cA);
BME280I2CSoftwareWire bme2(BusI2cB);
BME280I2CSoftwareWire bme3(BusI2cC);

//////////////////////////////////////////////////////////////////
void setup() { }
void loop() { delay(500); }

[finitespace]

#123