This is also my dilemma. I must have gone through the earlier chapters a (or two) dozen times.
Among the bugs, my original secondary plot line (packing orders at school) was too plain/happy/conflict-less and I'm revamping it, but every evening during shower (my brainstorm time) I'll figure out something wrong with my intended approach and thus its become an eternal back-and-forth struggle. I'm now trying to skip school plot and move on with the main plot. I'm not sure how this approach will work. It's kinda frustrating. I think I need more whiskey and ice cream.
The stinking shower gets me every time. I've rewritten the first two chapters of my WIP like ten times. I was thinking about it in the shower the other morning when the beginning popped in my head. I had repeat it over and over in my head while I hurried to rinse my hair so I could scribble it down before I forgot it. It's far from perfect, but it's finally in a place where I can move on and keep writing.
I think the key is not to lose momentum once you get it. You can always go back and revise later if you realize the beginning isn't quite right. That's what I keep having to tell myself.
Of course more whiskey and ice cream never hurts.