Help troubleshooting a DC power supply

[Fluxed Matter]

I picked up this power supply recently at a yard sale hoping I was getting a deal. It works and I started to do some preliminary testing. It was during that time that I found the problem. I was checking the voltages for overshoot when turning on the supply with my fluke using the min/max feature because I did not have a scope at the time. Well I was feeling kind of happy because fluke did not detect any overshoot but that is when I noticed that when the power supply is switched off there is a huge overshoot, I mean a large spike before it goes to 0V. I was testing the supply at 5V and when switched off the fluke recorded a maximum of 21V. Well last night, after finally getting a scope, I got the supply hooked it up to it and here is what I captured.

I tested the supply at various power settings such as 3.3, 5, 15, 20, 25 and the maximum of 30V. Here are just a few of the screenshots.


This leads me to my next questions. Has anyone seen this before? What was the problem? What should I start checking first?
 
All suggestions are welcome. Thank you.

[Rerouter]

based on the response i would imagine its the control loop powering down before the output falls, as its too well formed for an inductor,