I'm having some problem to detect slaves when I connect both but not when I connect only one. They have even the differents IDs and work individually but not work when they are together.

I'm using custom protocol to master-slaves communication, to use any pin that I need and to have completely free the I2C, SPI, UART... pins, to use without problems a MPU9265 (I2C) or ESP8266 (SPI)