Let me start by saying I have ceased the use of this outlet, and will be contacting maintenance for a replacement.
I have a grounded outlet in my apartment that has had a power strip plugged into it for nearly 2 years. The plug on the strip is 3 prong without the wider blade of a polarized plug. I believe I may have bumped the cord when I was running some cables nearby as the power strip had lost power. I checked the plug to find it ever so slightly tilted out of the socket (tipped down, pivoting on the ground prong if that matters). Upon tipping it back to be fully seated I heard the telltale sound of an arc happening.
I pulled the plug out and found a scorch mark on a very specific spot on the left prong. Upon re-seating the plug I heard it again. I shut off the strip and moved it to the plug above on the same outlet. I figured I had a bad connection in that particular socket, so I plugged in my lamp which has a polarized 2 prong plug. No issue. Not even when wiggling it.
So now I thought, well maybe only a non-polarized plug will have a bad connection due to the size. So I plugged in a simple night light. It has 2 prongs and is not polarized. Again, no issue. Regardless of the orientation or any wiggling.
So that leaves me wondering, what is so special about the power strip that makes it arc? Is it that it's grounded? Is it the amount of power being drawn?