a few mega1284p with RS422( addressed) modules connect on the same rs422 communication line, after power off/on ( slow ram up power supply), most time they all working fine, but a few times one module drop off, and never come back, no matter how many times reset.
verify the flash and eeprom to check firmware, there is no firmware corruption.
the fuse configure is:
re program the board, it back to work as normal.
any idea why it happened? is there anything with boot loader? Thanks