Wow! Looks like UV exposure but on the back against a receptacle, it's not likely. I don't see any signs of overheating from a loose connection and/or high loads.

You need to put some vaseline on the next plug inserted there and plug it in and out a few times to wipe it in. Silicone grease is even better if you have access to some. This can happen with aluminum against some other metals. They can bond after a time. 

 

Edited March 21, 20196 yr by larryllix

The plastic seems to be quite brittle. If you look at how the pins and PCB is fastened to the back piece. That could also put stress on the back if the pins are firmly held by the outlets socket connections.

I have worried about unplugging a few of mine. That seemed to be  resistant to removal from the outlet.

 

Edited March 21, 20196 yr by Brian H

It was in a closet that never saw sunlight but the plastic did behave like it was in the sun for 30 years. Smarthome had me remove the label to do an RMA and when I peeled off the label the plastic was so brittle that it broke into a hundred smaller pieces. Wasn't even 2 years old, whereas the older design that the PLM and IOLinc use is much stronger and has lasted years longer. I'm afraid of going around my house and unplugging all the other ON/OFF and lamplinc modules.

39 minutes ago, MustangChris04 said:

It was in a closet that never saw sunlight but the plastic did behave like it was in the sun for 30 years.

Was it hot when it was operating? Buried behind or underneath something?  Failure mode sounds like high temp, not UV, accelerated aging. Breakdown rate of most plastics is an exponential function of temperature.

Edited March 21, 20196 yr by palayman

On 3/21/2019 at 7:45 PM, palayman said:

Was it hot when it was operating? Buried behind or underneath something?  Failure mode sounds like high temp, not UV, accelerated aging. Breakdown rate of most plastics is an exponential function of temperature.

It doesn't get hotter than 80 degrees in the room it was in. Definitely not being covered by anything, as I'd be looking for trouble doing that. Insteon sent me a replacement this time no questions asked, whereas last year it was a different story. Maybe they've seen this more often now?

Even brand new out of the box the plastic is not forgiving at all, whereas the older styles are built like a tank.

I agree. The new plastic used in the present cases is not as good as the old plastic used in the older cases.