AT command port moved from ttyUSB2 to ttyUSB0


Hi I am using a EM7455 module on our custom ARM Linux platform.
The AT command communication is normally on /dev/ttyUSB2, but when I do a at+cfun=1,1 command to reset the module, when the module resets and comes back in about 30 secs, the port to communicate AT command got moved to /dev/ttyUSB0.

Why is this happening? It didn’t used to behave this way on my board.