Regulators that are old have parts that wear out. Eventually you
just have to replace them. Wear and tear on your soldering tools are
just like wear and tear on your car. Think of a 15 year old rubber
fan belt, or hoses. Risking a flaky regulator is not worth your life.
Good ones cost between $85 to $125 and that is a small price to pay
for you to continue and make jewelry.
Regulators should always be turned counter clockwise when you are
finished. This releases the stress and pressure on the regulator
diaphragm and places them in their relaxed sleep mode.
For your mini torch, it will cost more to repair than to replace it
and I would be surprised if the the knowledge to repair a mini torch
even exists any more.