The engineers should have learned from the mistakes with Galileo and Hubble. James Webb will hopefully not be delayed for a few years after it's ready like either mission, but any lubricant that is used would probably be double checked in that case. Also, the mirrors must have been more meticulously grounded than Hubble. What is really dangerous are the unforeseen issues, problems that have not occurred before and were never thought about. With such a complex spacecraft, there must be many of them which is scary.