I also bought a fitness machine with the same strategy. I repaired it myself after the spring broke today:
1, remove the spring. According to the tips on the stickers at both ends of the spring, it should be easy to remove.
2. After the spring is removed, there will be protruding parts at both ends, and there will be a disc in the middle, which will be stuck with transparent glue or sticky things. As soon as it is pulled, the disc will come down (the disc can be removed only by pressing both ends, but it cannot be sealed).
You can see that there is something similar to a rubber tube and a plastic needle with a square hole in it. The rubber tube inside is the built-in spring. You can pull out the rubber tube with needle-nosed pliers. Don't worry, it won't leave a scar.
4. Press all plastic bolts into the rubber tube, and all of them must be pressed in, so that both ends of the internal spring will be firmly stuck in the plastic heads at both ends. Then reset the wafer.
So it was fixed. Have a good exercise!