could you do a test to diagnose the functionality of the bus that reads the KCeptors?
Please connect to the RPI through SSH, plug only one KCeptor on any gate and run this line:
i2cset -y 1 0x70 0xff; i2cdetect -y 1
Repeat the operation with the same KC in the gate 5. Do you have a positive reading in the range [0x40,0x42]?