With these particular engines, you also have the variable factor of them being stored for decades in a warehouse, and all the issues with metal corrosion, fatig

With these particular engines, you also have the variable factor of them being stored for decades in a warehouse, and all the issues with metal corrosion, fatigue, degradation, etc. that come with that. I'm not a materials engineer, but I could imagine things like seasonal temperature changes, humidity, rough handling, changes in the metallurgical properties of the alloys they used over time could all affect the ability of the engine components to withstand high temperatures and pressures.