Those spring clips were stuck to the cenerting buttons when I did mine. By the time I was done one spring clip had fallen of where it seemed like it was glued on. I'm sure it was because of more than 40 years of being stuck together, it became one. I cleaned off the old grease and didn't remove the spring clip from the one button. Maybe yours was the same.
If you have no vibration your probably ok. If you ever come accross one with clips it wouldn't hurt to put them on.
