Thanks for reply, PCB is already designed so, we have to use it Software Serial for demo purpose,
and YES software Serial is not working it will stop listening RS485 commands and we need to restart device.
Right now i am testing the device on serial1, serial2 and serial3 port and its working fine.
Is it problem in Software Serial?
Means for production Software Serial is bad idea..
MCU = ATMEGA2560-AU