Stayed at a state park in OH this Fall and the 30a outlet was crispy, the only word that does it justice....not only was the 30a socket loose, the face of it was charred and there was smoke reside on the inside of the pedestal cover, so somebody toasted a cord or two there. I plugged my tester in, and if I didn't hold it a certain way I lost the neutral. There was no 50a service available, and fortunately I didn't need a/c so I just plugged into the 20a service.
Sometimes you can bend the prongs on the plug either closer together or further apart so they make better contact with the contacts inside the receptacle...which way you bend them depends on which side of the slots the contacts are on inside the receptacle. This is only a temp emergency fix...I wouldn't recommend bending your plug prongs regularly.
I like the 30-30 pigtail, thanks for posting that. Sort of a sacrificial cord.