Odd WS-12-250-DC Failures

[dpwii]

A week ago I had a WS-12-250-DC that went dead for no apparent reason.
I doubt this was a surge because it was sunny and nice at the time it failed.
Anyway, I took one of my 2 new spares off the shelf, updated and programmed it.
I took it to the site and swapped them out. The replacement worked fine for about 5 minutes and then completely died.
BTW, I'm always careful not to plug or unplug anything with the power on.
After removing and re-applying power the green light would come on and stay.
The fans never would run like they normally do on startup.
I installed some AC PoE supplies I keep on site for emergencies like this.
Everything is working fine on the original PoE injectors. I meant to RMA both switches, but I got busy and forgot.

Last night I had a different site go down. Turned out to be a completely dead WS-12_250 DC. This one was probably damaged by a surge.
I took the second new spare updated and programmed it. I got to the site and found no green light on the bad switch.
First thing I did was verify 13.9 volts DC on the terminals and very little ripple (15 mV).
I connected all of the network cables and applied power to the replacement.

Everything worked fine for about 5 minutes. Then the replacement went dead.
Removing and reapplying power made no difference.
The green light would light for a few second and then go out.
I installed the original AC PoE injectors and got everything back online again.
Everything is still working fine on the old injectors.

I know what killed one of them.
Any Ideas what might have happened to the others??
Looks like I need to RMA 4 switches.

[sirhc]

I really can not tell without looking at them, sorry.

Once we see them we can tell you within a pretty decent amount of certainty the issue.

We were really behind in RMA's due to the 3 Hurricanes and the related damage but Julian is seeing the light at the end of the tunnel.