Yamaha CS80

In my experience, double triggering occurs mostly when releasing a key. 
I think releasing a key takes a bit more time than pressing a key 
during normal playing. At a certain point, there's a moment the right 
spring-leave stops touching it's upper contact spring and a fraction of 
a key-movement later it touches it again. This can be caused by a dirty 
contact-surface, or the contact surfaces have blind spots, one or both 
of the right spring-contacts are a bit tordated etc.

Till now, I am able to reduce double triggering by cleaning the contact-
area and some very slight bending/tordating of the 2 right contact-
springs and checking their behavour while very slowely releasing the 
key.

In my opinion, if not all keys cause double-triggering then it's not 
needed to modify the electronic circuity, just cure the keys that are 
causing problems.