I have nine M5s, three connected via Ethernet. They have worked flawlessly for over two years.

One wired M5 started losing its connection, flashing red. I did resets, firmware, etc., and it still dropped off about every hour or so and then come back online. There was nothing glaring in the log other than the disconnects. I replaced the cable, etc., and the drop-off/flashing red also occurred non-wired.

I replaced the unit and everything has worked fine for close to a week. 

Other than resets, is there anything I can do to see if I can save this unit? It is 2.5 years old.