I recently ran into a problem with the CSS106-5g-1s switch. I had it connected to an RB5009 router via SFP and a HAP ax2 on port 1 via cat5 to port 1 of the switch.
I ran a remote upgrade of the HAP which completed fine, then tried to upgrade SwOS from 2.16 to 2.18 which failed. When I got onsite I could not connect to the switch locally. I noticed the ethernet light for port1 on the switch was blinking, but the SFP light was not. Pings were at 90+% loss to the switch.
The HAP was showing the red PoE light as on which was not the case when originally installed.
I moved the ethernet cable from port 1 of both devices to port 5 and power cycled. After that I was able to log into the switch which appeared to be using a backup firmware as it was requesting that it be upgraded. I ran the upgrade to 2.18 and everything worked fine after that.
I’m not sure if the PoE was the issue or if it was the failed firmware upgrade, but the solid, non-blinking SFP light made me think that something was wrong besides just the backup firmware. I don’t know if anyone has run into this before, but I thought I’d post it just in case. It seems like the switch should handle power from the PoE and the wall adapter at the same time with no issue, but maybe there is an unexpected failure mode hidden there.