Arduino Rs485 Serial Communication Problems

Hello friends
I have a new RS485 serial communication line.
I did it from the sources I found on the internet.
The system works fine for 15 or 20 days but after a while I break the nport 5150 device that I use as a converter. I can not find where the problem originated. There are 32 arduos on one line. None of them are faulty. I am waiting for your help