i dont believe the spring is being effected by heat... its a formed spring and engine temps are no where near what they would be tempered at...
BUT
I do think springs once compressed will relax after initial use and settle.. which is the more likely cause for change to me
that
video you posted above is exactly what I was describing to you... Great vid.. comfirms what happens when the nozzles too outboard of the hole its sat in.. The spray cone which is usually less than 90 degrees (and varies with manufacturer I might add) could catch the hole on the way out if not flush with the pipe ID, cause drop out.