This is tough, i have never personally replaced these as they are incredibly dangerous. It may not seem tight but it IS. Normally if the spring is shot I just replace the outer casing, if you would like one, i can probably get you one.
Since it is not broken, can you reshape the tab using a drift punch and a hammer?
You might need to wedge a small flat blade screwdriver between the case and the stop to get a gap between them first.
If you think you're having trouble with the handle fork spring, order part no. 137073 (for models Classic Omega to Legend II) but beware: to remove it is a very tedious process.