I believe, that RS-485 can cause such problems (and many others).

But I use CAN and it works very nice.
Every device has its own Dallas serial number chip with its own serial number world wide.

So on a request several devices can answer with its own 7 byte serial number.

And with using CAN there is no problem, that absolute every device on the bus can send its serial number to the master. Since the CAN solve the arbitration fully automatically and no packet was lost.

Thus I suggest to put away the antiquated RS-485 and switch to the modern, easy and reliable CAN.


Peter