I2C question about 2 Channel CAN BUS FD Shield for Raspberry Pi

Hi everyone, I use raspberry pi 3B+ with the latest raspbian system. I found that it was strange when I connect only one i2c slave device to CAN BUS FD Shield for Raspberry Pi. I use i2cdetect command and it did not find the device which is a joystick with grove interface, however when I plug two device into the i2c slot it find the device.

I also tried directly connect one device to the I2C pins of raspberry pi and it worked right. So I don’t know where the problem is. It’s confusing.