this image shows a gearbox with its shift counterweight
the spring should be on the pivot of the counterweight
the other possibility is that the plastic part of the cable is broken or flexing in which case you have to replace the whole cable
procdure for that is :
remove the battery, battery cover and box, air filter assembly, battery tray (mostly bolts in the top of the tray but there's one really annoying one which you have to remove the wheel inner trim for and get to from the wheel arch)
Once the battery tray is removed its easy to get to the top of the gear linkage and take the cables off.
The reverse cable requires a torx tool and you need to go through the wheel arch again - no drilling, the bolt is quite visible and easy to access.
This part pops out of the gearbox housing with a little force. Once done with that, the outer cables will need to be removed from the holders, the metal clips are stiff but will come out with some wiggling and a tiny flat blade screwdriver.
If you put string around the cable ends you can then feed the new cables through
Moving to the inside, the centre console needs to be unscrewed and taken up (but not off). The gear gaiter needs to be taken up and the bolts from the gearstick housing off.
Then remove the heater ducts from either side of the gearstick housing area.
There was a rectangular connector which if removed will create a lot more room.
Pull the gearstick up and backwards whilst lifting the centre console.
This should give you enough room to get to the rubber gaiter which the cables go through. if you look under the car and remove a plastic clip that retains the gaiter
Then you should find the whole assembly comes out from the engine bay, whilst still lifting the centre console and doing a bit of jiggery pokery. You should then be able to completely remove the cables and stick from the car and start to install the new one. Use the string to pull the new cables back through, use a LOT of lube on the new gaiter and bash it in with a rubber mallet and stick wide enough to "push" it into place. Dont forget to use plenty of suitable grease on the ball joints. Installing is pretty much reverse of removal, but a lot quicker.