After many years old dropouts tend to polish & slip on the derailleur side. A solution that
worked really well for me : I took a used 3/4" diamond disc wheel from my dremel, bored
it out to where a skewer would fit through it. Instead of a spring on that side, I use it as
a washer to grip the dropout. These discs are not expensive, something like $6 for 4 from
Widget Supply.com. I've got 'em on all my old bikes.(this to say all my bikes are old)




Warning: Cycling maybe be frustrating for the mechanically challenged