Even Leo Rosten’s “The New Joys of Yiddish,” whose earlier edition is used by many as an authority on spelling Yiddish words commonly used in America, throws its hands up in surrender: “The proper transliteration of this festival’s name remains one of the great mysteries of modern Jewish life,” it says.
There is no correct way to spell a transliterated word. I've always spelt the festival "Chanukah" although I say "ħanukeh". Yiddish has so many dialects that I have rarely heard two people speak the same way.
My zajda was from a different part of Europe to my teachers at Sholem Aleichem College. I ended up with a confused pronunciation based on who managed to get the word in my brain first.
I remember a teacher in prep or grade 1 trying to get me to pronounce the Yiddish word for chicken soup the same way she did. I refused. To this day it is "yo-eħ" and will never be "yoiħ" as long as it comes from my lips and tongue.
Yiddish pronunciation is a lot like chicken soup: everybody's grandmother did it the best way.
On the other hand, the spelling of transliterated words is only correct if the person reading it can approximate the same sounds out loud. Therefore knaidel, kneidel and kneydl are all correct enough as long as they are not too dense and add a decent mouth-feel to the yoech.