Can you swap tension spring from another location to eliminate that as a potential problem?

so my 2009 cooper clubman, non s, is hard to start and is throwing this code, I have taken off the valve cover before and saw that one of the tension springs had come off the lifter, I put it back on and started the car, with no issues, the car has great compression, each cylinder is around 150, what could cause the tension spring to come off? I have a feeling it came off again today as I heard a crack noise coming from the engine and cylinder 4 is misfiring again, how can I fix this problem...