what did i do wrong? Cleaned auto select on astra 98 now car starts temprem?

I had the flashing S od doom so, I removed, cleaned & put back the auto select switch as it was fully gunked up & causing sluggish gear changes. Car works perfectly now & changes gears smoothly with good take off. But now it is tempremental when starting in P, it's like i'm trying to start it in 'D' (i'm not) so to get it to start, I have to rock the level from 1 back to P then start it. (doesn't always work) but gets there in the end. What have I done wrong? I put it back exactly as I took it off. Really wasn't that hard to clean at all. But fear i have messed something up? Anyhelp much appreciated. PS it's a 98 astra 1,6 auto.