Hrrrrrrmm...
For this to happen, the spring has to be sticky or being compressed to the point of latching itself.
It's also possible that that batch of springs were too tightly wound.
Can you take a picture from Top down of the affected spring, Uncompressed, and 1 fully depressed with a tooth pick ..
Also, the back of the silicone cup , is it slightly sticky or has any residue. ??
If the silicone sheet former is ran too hot, there could be residue.
If the spring extruder was over-lubed, there could be grease residue on the spring.
If they messed up the formula for the silicone sheets for a batch, the surface might've degraded becoming sticky.